![\"Whimsical](\"https:\/\/www.viz-read.com\/wp-content\/uploads\/2026\/03\/7-erd-mistakes-database-design-whimsical-infographic.jpg\"\/)
<\/figure>\n<\/div>\n1. Thi\u1ebfu ho\u1eb7c Kh\u00f3a Ch\u00ednh Y\u1ebfu \ud83d\udd11<\/h2>\n
Kh\u00f3a ch\u00ednh l\u00e0 \u0111\u1ecbnh danh duy nh\u1ea5t cho m\u1ed9t b\u1ea3n ghi trong m\u1ed9t b\u1ea3ng. N\u00f3 l\u00e0 \u0111i\u1ec3m t\u1ef1a \u0111\u1ea3m b\u1ea3o m\u1ecdi h\u00e0ng \u0111\u1ec1u kh\u00e1c bi\u1ec7t v\u00e0 c\u00f3 th\u1ec3 truy xu\u1ea5t \u0111\u01b0\u1ee3c. B\u1ecf qua kh\u00f3a ch\u00ednh ho\u1eb7c thi\u1ebft k\u1ebf n\u00f3 k\u00e9m hi\u1ec7u qu\u1ea3 l\u00e0 m\u1ed9t trong nh\u1eefng l\u1ed7i c\u01a1 b\u1ea3n nh\u1ea5t trong ki\u1ebfn tr\u00fac c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/p>\n
H\u1eadu qu\u1ea3 K\u1ef9 thu\u1eadt<\/h3>\n\n- Sao ch\u00e9p D\u1eef li\u1ec7u:<\/strong>Kh\u00f4ng c\u00f3 r\u00e0ng bu\u1ed9c duy nh\u1ea5t, c\u01a1 s\u1edf d\u1eef li\u1ec7u kh\u00f4ng th\u1ec3 ng\u0103n ch\u1eb7n c\u00e1c b\u1ea3n ghi tr\u00f9ng l\u1eb7p. \u0110i\u1ec1u n\u00e0y d\u1eabn \u0111\u1ebfn b\u00e1o c\u00e1o kh\u00f4ng nh\u1ea5t qu\u00e1n v\u00e0 c\u00e1c v\u1ea5n \u0111\u1ec1 v\u1ec1 t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u.<\/li>\n
- Hi\u1ec7u su\u1ea5t Join:<\/strong>C\u00e1c m\u1ed1i quan h\u1ec7 kh\u00f3a ngo\u1ea1i ph\u1ee5 thu\u1ed9c v\u00e0o kh\u00f3a ch\u00ednh \u0111\u1ec3 l\u1eadp ch\u1ec9 m\u1ee5c hi\u1ec7u qu\u1ea3. Kh\u00f3a ch\u00ednh b\u1ecb thi\u1ebfu ho\u1eb7c kh\u00f4ng \u0111\u01b0\u1ee3c ch\u1ec9 m\u1ee5c s\u1ebd bu\u1ed9c ph\u1ea3i qu\u00e9t to\u00e0n b\u1ed9 b\u1ea3ng trong c\u00e1c thao t\u00e1c join, l\u00e0m ch\u1eadm \u0111\u00e1ng k\u1ec3 vi\u1ec7c th\u1ef1c thi truy v\u1ea5n.<\/li>\n
- \u0110\u1ed9 ph\u1ee9c t\u1ea1p C\u1eadp nh\u1eadt:<\/strong>N\u1ebfu b\u1ea1n c\u1ea7n c\u1eadp nh\u1eadt m\u1ed9t b\u1ea3n ghi, h\u1ec7 th\u1ed1ng ph\u1ea3i d\u1ef1a v\u00e0o c\u00e1c c\u1ed9t kh\u00f4ng duy nh\u1ea5t \u0111\u1ec3 t\u00ecm h\u00e0ng. N\u1ebfu nhi\u1ec1u h\u00e0ng kh\u1edbp v\u1edbi ti\u00eau ch\u00ed t\u00ecm ki\u1ebfm, thao t\u00e1c c\u1eadp nh\u1eadt c\u00f3 th\u1ec3 \u00e1p d\u1ee5ng cho d\u1eef li\u1ec7u kh\u00f4ng mong mu\u1ed1n.<\/li>\n<\/ul>\n
Th\u1ef1c h\u00e0nh T\u1ed1t \u0111\u1ec3 Tr\u00e1nh L\u1ed7i N\u00e0y<\/h3>\n\n- Lu\u00f4n \u0111\u1ecbnh ngh\u0129a kh\u00f3a ch\u00ednh cho m\u1ecdi b\u1ea3ng, ngay c\u1ea3 khi n\u00f3 c\u00f3 v\u1ebb th\u1eeba.<\/li>\n
- \u01afu ti\u00ean s\u1eed d\u1ee5ng kh\u00f3a gi\u1ea3 (s\u1ed1 nguy\u00ean t\u1ef1 t\u0103ng ho\u1eb7c UUID) thay v\u00ec kh\u00f3a t\u1ef1 nhi\u00ean (nh\u01b0 \u0111\u1ecba ch\u1ec9 email ho\u1eb7c s\u1ed1 \u0111i\u1ec7n tho\u1ea1i) \u0111\u1ec3 tr\u00e1nh vi\u1ec7c thay \u0111\u1ed5i logic kinh doanh \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn l\u01b0\u1ee3c \u0111\u1ed3.<\/li>\n
- \u0110\u1ea3m b\u1ea3o c\u1ed9t kh\u00f3a ch\u00ednh kh\u00f4ng \u0111\u01b0\u1ee3c ph\u00e9p null.<\/li>\n
- Ch\u1ec9 s\u1eed d\u1ee5ng kh\u00f3a h\u1ee3p th\u00e0nh khi m\u1ed9t c\u1ed9t duy nh\u1ea5t kh\u00f4ng th\u1ec3 x\u00e1c \u0111\u1ecbnh duy nh\u1ea5t m\u1ed9t h\u00e0ng, v\u00ed d\u1ee5 nh\u01b0 trong c\u00e1c b\u1ea3ng quan h\u1ec7 nhi\u1ec1u-nhi\u1ec1u.<\/li>\n<\/ul>\n
2. Cardinality M\u1ed1i quan h\u1ec7 M\u1eadp m\u1edd \ud83d\udd04<\/h2>\n
Cardinality x\u00e1c \u0111\u1ecbnh m\u1ed1i quan h\u1ec7 s\u1ed1 l\u01b0\u1ee3ng gi\u1eefa c\u00e1c b\u1ea3n ghi trong hai b\u1ea3ng. C\u00e1c lo\u1ea1i ph\u1ed5 bi\u1ebfn bao g\u1ed3m m\u1ed9t-\u0111\u1ed1i-m\u1ed9t, m\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u v\u00e0 nhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u. Bi\u1ec3u di\u1ec5n sai c\u00e1c m\u1ed1i quan h\u1ec7 n\u00e0y trong s\u01a1 \u0111\u1ed3 s\u1ebd d\u1eabn \u0111\u1ebfn s\u1ef1 kh\u00f4ng kh\u1edbp c\u1ea5u tr\u00fac trong c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u1eadt l\u00fd.<\/p>\n
Nh\u1eefng Sai L\u1ea7m Ph\u1ed5 Bi\u1ebfn<\/h3>\n\n- Gi\u1ea3 \u0111\u1ecbnh M\u1ed9t-\u0110\u1ed1i-Nhi\u1ec1u:<\/strong>C\u00e1c nh\u00e0 thi\u1ebft k\u1ebf th\u01b0\u1eddng m\u1eb7c \u0111\u1ecbnh m\u1ed1i quan h\u1ec7 m\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u khi th\u1ef1c t\u1ebf l\u00e0 nhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u. V\u00ed d\u1ee5, m\u1ed9t sinh vi\u00ean c\u00f3 th\u1ec3 \u0111\u0103ng k\u00fd nhi\u1ec1u kh\u00f3a h\u1ecdc, v\u00e0 m\u1ed9t kh\u00f3a h\u1ecdc c\u00f3 th\u1ec3 c\u00f3 nhi\u1ec1u sinh vi\u00ean. M\u00f4 h\u00ecnh h\u00f3a \u0111i\u1ec1u n\u00e0y d\u01b0\u1edbi d\u1ea1ng m\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u s\u1ebd y\u00eau c\u1ea7u sao ch\u00e9p d\u1eef li\u1ec7u sinh vi\u00ean tr\u00ean nhi\u1ec1u h\u00e0ng kh\u00f3a h\u1ecdc.<\/li>\n
- C\u00e1c \u0111\u01b0\u1eddng n\u1ed1i Kh\u00f4ng Nh\u00e3n:<\/strong>C\u00e1c \u0111\u01b0\u1eddng n\u1ed1i trong ERD n\u00ean th\u1ec3 hi\u1ec7n cardinality (v\u00ed d\u1ee5 nh\u01b0 k\u00fd hi\u1ec7u ch\u00e2n chim). B\u1ecf tr\u1ed1ng nh\u00e3n s\u1ebd khi\u1ebfn c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n ph\u1ea3i \u0111o\u00e1n c\u00e1ch d\u1eef li\u1ec7u li\u00ean h\u1ec7 v\u1edbi nhau.<\/li>\n
- B\u1ecf qua Kh\u1ea3 n\u0103ng Null:<\/strong>M\u1ed1i quan h\u1ec7 m\u1ed9t-\u0111\u1ed1i-m\u1ed9t c\u00f3 th\u1ec3 cho ph\u00e9p c\u00e1c gi\u00e1 tr\u1ecb null trong c\u1ed9t kh\u00f3a ngo\u1ea1i n\u1ebfu m\u1ed1i quan h\u1ec7 l\u00e0 t\u00f9y ch\u1ecdn. Kh\u00f4ng m\u00f4 h\u00ecnh h\u00f3a r\u00e0ng bu\u1ed9c n\u00e0y s\u1ebd cho ph\u00e9p t\u1ed3n t\u1ea1i c\u00e1c b\u1ea3n ghi b\u1ecb b\u1ecf r\u01a1i.<\/li>\n<\/ul>\n
C\u00e1ch Ti\u1ebfp C\u1eadn \u0110\u00fang<\/h3>\n\n- M\u00f4 h\u00ecnh h\u00f3a r\u00f5 r\u00e0ng c\u00e1c m\u1ed1i quan h\u1ec7 nhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng b\u1ea3ng giao nhau (b\u1ea3ng li\u00ean k\u1ebft) ch\u1ee9a c\u00e1c kh\u00f3a ngo\u1ea1i t\u1eeb c\u1ea3 hai b\u1ea3ng li\u00ean quan.<\/li>\n
- Ghi r\u00f5 cardinality tr\u00ean c\u00e1c \u0111\u01b0\u1eddng n\u1ed1i trong s\u01a1 \u0111\u1ed3.<\/li>\n
- \u00c1p d\u1ee5ng c\u00e1c r\u00e0ng bu\u1ed9c c\u01a1 s\u1edf d\u1eef li\u1ec7u (nh\u01b0 r\u00e0ng bu\u1ed9c UNIQUE tr\u00ean kh\u00f3a ngo\u1ea1i) \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o logic trong s\u01a1 \u0111\u1ed3 \u0111\u01b0\u1ee3c th\u1ef1c thi.<\/li>\n<\/ul>\n
\n\n\nLo\u1ea1i quan h\u1ec7<\/th>\n Chi\u1ebfn l\u01b0\u1ee3c tri\u1ec3n khai<\/th>\n L\u1ed7i ph\u1ed5 bi\u1ebfn<\/th>\n<\/tr>\n<\/thead>\n \n\nM\u1ed9t-\u0111\u1ed1i-m\u1ed9t<\/td>\n Kh\u00f3a ngo\u1ea1i trong m\u1ed9t b\u1ea3ng v\u1edbi r\u00e0ng bu\u1ed9c UNIQUE<\/td>\n Th\u00eam kh\u00f3a ngo\u1ea1i v\u00e0o c\u1ea3 hai b\u1ea3ng m\u1ed9t c\u00e1ch kh\u00f4ng c\u1ea7n thi\u1ebft<\/td>\n<\/tr>\n \nM\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u<\/td>\n Kh\u00f3a ngo\u1ea1i trong b\u1ea3ng \u201cNhi\u1ec1u\u201d<\/td>\n L\u01b0u tr\u1eef d\u1eef li\u1ec7u cha trong b\u1ea3ng con (phi chu\u1ea9n h\u00f3a)<\/td>\n<\/tr>\n \nNhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u<\/td>\n B\u1ea3ng li\u00ean k\u1ebft trung gian<\/td>\n L\u01b0u tr\u1eef nhi\u1ec1u ID trong m\u1ed9t c\u1ed9t ph\u00e2n c\u00e1ch b\u1eb1ng d\u1ea5u ph\u1ea9y<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n3. B\u1ecf qua c\u00e1c ti\u00eau chu\u1ea9n chu\u1ea9n h\u00f3a \ud83d\udcc9<\/h2>\n
Chu\u1ea9n h\u00f3a l\u00e0 qu\u00e1 tr\u00ecnh t\u1ed5 ch\u1ee9c d\u1eef li\u1ec7u nh\u1eb1m gi\u1ea3m thi\u1ec3u s\u1ef1 tr\u00f9ng l\u1eb7p v\u00e0 c\u1ea3i thi\u1ec7n t\u00ednh to\u00e0n v\u1eb9n. Trong khi m\u1ed9t s\u1ed1 h\u1ec7 th\u1ed1ng hi\u1ec7n \u0111\u1ea1i ch\u1ea5p nh\u1eadn phi chu\u1ea9n h\u00f3a \u0111\u1ec3 t\u0103ng hi\u1ec7u su\u1ea5t \u0111\u1ecdc, nh\u01b0ng b\u1ecf qua ho\u00e0n to\u00e0n chu\u1ea9n h\u00f3a trong giai \u0111o\u1ea1n thi\u1ebft k\u1ebf s\u1ebd t\u1ea1o ra g\u00e1nh n\u1eb7ng b\u1ea3o tr\u00ec \u0111\u00e1ng k\u1ec3.<\/p>\n
R\u1ee7i ro c\u1ee7a vi\u1ec7c chu\u1ea9n h\u00f3a k\u00e9m<\/h3>\n\n- L\u1ed7i c\u1eadp nh\u1eadt:<\/strong> N\u1ebfu \u0111\u1ecba ch\u1ec9 kh\u00e1ch h\u00e0ng \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef trong n\u0103m b\u1ea3ng \u0111\u01a1n h\u00e0ng kh\u00e1c nhau, vi\u1ec7c c\u1eadp nh\u1eadt \u0111\u1ecba ch\u1ec9 c\u1ee7a h\u1ecd \u0111\u00f2i h\u1ecfi n\u0103m thao t\u00e1c c\u1eadp nh\u1eadt ri\u00eang bi\u1ec7t. N\u1ebfu m\u1ed9t thao t\u00e1c th\u1ea5t b\u1ea1i, d\u1eef li\u1ec7u s\u1ebd tr\u1edf n\u00ean kh\u00f4ng nh\u1ea5t qu\u00e1n.<\/li>\n
- L\u1ed7i ch\u00e8n:<\/strong> B\u1ea1n c\u00f3 th\u1ec3 kh\u00f4ng th\u1ec3 th\u00eam m\u1ed9t danh m\u1ee5c s\u1ea3n ph\u1ea9m m\u1edbi m\u00e0 kh\u00f4ng c\u1ea7n th\u00eam b\u1ea3n ghi s\u1ea3n ph\u1ea9m, bu\u1ed9c ph\u1ea3i t\u1ea1o d\u1eef li\u1ec7u gi\u1ea3.<\/li>\n
- L\u1ed7i x\u00f3a:<\/strong> Vi\u1ec7c x\u00f3a m\u1ed9t b\u1ea3n ghi c\u00f3 th\u1ec3 v\u00f4 t\u00ecnh lo\u1ea1i b\u1ecf d\u1eef li\u1ec7u quan tr\u1ecdng li\u00ean quan \u0111\u1ebfn c\u00e1c th\u1ef1c th\u1ec3 kh\u00e1c.<\/li>\n<\/ul>\n
H\u01b0\u1edbng d\u1eabn tri\u1ec3n khai<\/h3>\n\n- M\u1ee5c ti\u00eau h\u01b0\u1edbng t\u1edbi d\u1ea1ng chu\u1ea9n h\u00f3a th\u1ee9 ba (3NF) nh\u01b0 m\u1ed9t n\u1ec1n t\u1ea3ng. \u0110i\u1ec1u n\u00e0y \u0111\u1ea3m b\u1ea3o r\u1eb1ng c\u00e1c c\u1ed9t ch\u1ec9 ph\u1ee5 thu\u1ed9c v\u00e0o kh\u00f3a ch\u00ednh.<\/li>\n
- X\u00e1c \u0111\u1ecbnh c\u00e1c ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u n\u01a1i m\u1ed9t c\u1ed9t kh\u00f4ng ph\u1ea3i kh\u00f3a ph\u1ee5 thu\u1ed9c v\u00e0o m\u1ed9t c\u1ed9t kh\u00f4ng ph\u1ea3i kh\u00f3a kh\u00e1c.<\/li>\n
- T\u00e1ch bi\u1ec7t c\u00e1c th\u1ef1c th\u1ec3 ri\u00eang bi\u1ec7t. N\u1ebfu m\u1ed9t b\u1ea3ng ch\u1ee9a th\u00f4ng tin v\u1ec1 c\u1ea3 \u201c\u0110\u01a1n h\u00e0ng\u201d v\u00e0 \u201cKh\u00e1ch h\u00e0ng\u201d, h\u00e3y t\u00e1ch ch\u00fang ra.<\/li>\n
- Ch\u1ec9 phi chu\u1ea9n h\u00f3a sau khi ph\u00e2n t\u00edch hi\u1ec7u su\u1ea5t truy v\u1ea5n. \u0110\u1eebng t\u1ed1i \u01b0u h\u00f3a tr\u01b0\u1edbc cho t\u1ed1c \u0111\u1ed9 m\u00e0 \u0111\u00e1nh \u0111\u1ed5i t\u00ednh to\u00e0n v\u1eb9n.<\/li>\n<\/ul>\n
4. T\u1ea1o ra c\u00e1c ph\u1ee5 thu\u1ed9c v\u00f2ng l\u1eb7p \ud83d\udd01<\/h2>\n
C\u00e1c ph\u1ee5 thu\u1ed9c v\u00f2ng x\u1ea3y ra khi c\u00e1c b\u1ea3ng tham chi\u1ebfu l\u1eabn nhau theo m\u1ed9t v\u00f2ng l\u1eb7p, ng\u0103n c\u1ea3n qu\u00e1 tr\u00ecnh kh\u1edfi t\u1ea1o ho\u1eb7c g\u00e2y ra \u0111\u1ec7 quy v\u00f4 h\u1ea1n trong truy v\u1ea5n. M\u1eb7c d\u00f9 c\u00e1c m\u1ed1i quan h\u1ec7 \u0111\u1ec7 quy (nh\u01b0 s\u01a1 \u0111\u1ed3 t\u1ed5 ch\u1ee9c n\u01a1i m\u1ed9t nh\u00e2n vi\u00ean c\u00f3 ng\u01b0\u1eddi qu\u1ea3n l\u00fd) l\u00e0 h\u1ee3p l\u1ec7, nh\u01b0ng c\u00e1c kh\u00f3a ngo\u1ea1i v\u00f2ng l\u1eb7p kh\u00f4ng ki\u1ec3m so\u00e1t \u0111\u01b0\u1ee3c c\u00f3 th\u1ec3 l\u00e0m h\u1ecfng c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/p>\n
T\u1ea1i sao \u0111i\u1ec1u n\u00e0y l\u00e0m h\u1ecfng h\u1ec7 th\u1ed1ng<\/h3>\n\n- L\u1ed7i kh\u1edfi t\u1ea1o:<\/strong> Trong qu\u00e1 tr\u00ecnh tri\u1ec3n khai, b\u1ed9 \u0111\u1ed9ng c\u01a1 c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u00f3 th\u1ec3 t\u1eeb ch\u1ed1i vi\u1ec7c t\u1ea1o r\u00e0ng bu\u1ed9c kh\u00f3a ngo\u1ea1i n\u1ebfu t\u1ed3n t\u1ea1i tham chi\u1ebfu v\u00f2ng l\u1eb7p (v\u00ed d\u1ee5: B\u1ea3ng A tham chi\u1ebfu B, v\u00e0 B tham chi\u1ebfu A) tr\u1eeb khi \u0111\u01b0\u1ee3c x\u1eed l\u00fd b\u1eb1ng c\u00e1c r\u00e0ng bu\u1ed9c ho\u00e3n l\u1ea1i.<\/li>\n
- Tr\u00e0n ng\u0103n x\u1ebfp truy v\u1ea5n:<\/strong>C\u00e1c truy v\u1ea5n \u0111\u1ec7 quy \u0111i qua nh\u1eefng v\u00f2ng l\u1eb7p n\u00e0y m\u00e0 kh\u00f4ng c\u00f3 \u0111i\u1ec1u ki\u1ec7n d\u1eebng c\u00f3 th\u1ec3 ti\u00eau th\u1ee5 to\u00e0n b\u1ed9 b\u1ed9 nh\u1edb s\u1eb5n c\u00f3.<\/li>\n
- Vi ph\u1ea1m t\u00ednh to\u00e0n v\u1eb9n tham chi\u1ebfu:<\/strong>X\u00f3a b\u1ea3ng cha c\u00f3 th\u1ec3 th\u1ea5t b\u1ea1i n\u1ebfu c\u00e1c b\u1ea3ng con ch\u01b0a \u0111\u01b0\u1ee3c d\u1ecdn d\u1eb9p, nh\u01b0ng vi\u1ec7c d\u1ecdn d\u1eb9p c\u00e1c b\u1ea3ng con c\u0169ng c\u00f3 th\u1ec3 th\u1ea5t b\u1ea1i do c\u00e1c ph\u1ee5 thu\u1ed9c kh\u00e1c.<\/li>\n<\/ul>\n
C\u00e1ch kh\u1eafc ph\u1ee5c<\/h3>\n\n- S\u1eed d\u1ee5ng R\u00e0ng bu\u1ed9c ho\u00e3n l\u1ea1i<\/strong> n\u1ebfu c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n h\u1ed7 tr\u1ee3 ch\u00fang, cho ph\u00e9p c\u01a1 s\u1edf d\u1eef li\u1ec7u ki\u1ec3m tra c\u00e1c m\u1ed1i quan h\u1ec7 sau khi t\u1ea5t c\u1ea3 d\u1eef li\u1ec7u \u0111\u00e3 \u0111\u01b0\u1ee3c t\u1ea3i.<\/li>\n
- \u0110\u1ed1i v\u1edbi c\u00e1c b\u1ea3ng tham chi\u1ebfu t\u1ef1 th\u00e2n (nh\u01b0 danh m\u1ee5c), \u0111\u1ea3m b\u1ea3o kh\u00f3a ngo\u1ea1i c\u00f3 th\u1ec3 \u0111\u1ec3 tr\u1ed1ng \u0111\u1ec3 cho ph\u00e9p c\u00e1c n\u00fat g\u1ed1c.<\/li>\n
- Thi\u1ebft k\u1ebf l\u01b0\u1ee3c \u0111\u1ed3 \u0111\u1ec3 cho ph\u00e9p m\u1ed9t c\u1ea5u tr\u00fac ph\u00e2n c\u1ea5p logic m\u00e0 kh\u00f4ng bu\u1ed9c ph\u1ea3i c\u00f3 v\u00f2ng l\u1eb7p kh\u00f3a ngo\u1ea1i v\u1eadt l\u00fd \u1edf m\u1ecdi c\u1ea5p \u0111\u1ed9.<\/li>\n
- Th\u1ef1c hi\u1ec7n x\u00f3a m\u1ec1m \u0111\u1ec3 qu\u1ea3n l\u00fd c\u00e1c thao t\u00e1c x\u00f3a lan truy\u1ec1n m\u1ed9t c\u00e1ch an to\u00e0n.<\/li>\n<\/ul>\n
5. Quy \u01b0\u1edbc \u0111\u1eb7t t\u00ean kh\u00f4ng nh\u1ea5t qu\u00e1n \ud83d\udcdd<\/h2>\n
T\u00ean l\u00e0 giao di\u1ec7n gi\u1eefa con ng\u01b0\u1eddi v\u00e0 m\u00e1y m\u00f3c. Vi\u1ec7c \u0111\u1eb7t t\u00ean kh\u00f4ng nh\u1ea5t qu\u00e1n trong t\u00ean b\u1ea3ng v\u00e0 c\u1ed9t khi\u1ebfn l\u01b0\u1ee3c \u0111\u1ed3 tr\u1edf n\u00ean kh\u00f3 hi\u1ec3u, kh\u00f3 b\u1ea3o tr\u00ec v\u00e0 truy v\u1ea5n. \u0110i\u1ec1u n\u00e0y th\u01b0\u1eddng xu\u1ea5t ph\u00e1t t\u1eeb vi\u1ec7c thi\u1ebfu m\u1ed9t h\u01b0\u1edbng d\u1eabn phong c\u00e1ch chung.<\/p>\n
C\u00e1c v\u1ea5n \u0111\u1ec1 c\u1ee5 th\u1ec3<\/h3>\n\n- Nhi\u1ec1u ch\u1eef hoa v\u00e0 th\u01b0\u1eddng:<\/strong>Pha tr\u1ed9n
camelCase<\/code>, snake_case<\/code>, v\u00e0 PascalCase<\/code> khi\u1ebfn c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n khi truy v\u1ea5n d\u1eef li\u1ec7u b\u1ecb nh\u1ea7m l\u1eabn.<\/li>\n- T\u1eeb kh\u00f3a \u0111\u01b0\u1ee3c b\u1ea3o l\u01b0u:<\/strong> S\u1eed d\u1ee5ng t\u00ean nh\u01b0
order<\/code>, group<\/code>, ho\u1eb7c user<\/code> m\u00e0 kh\u00f4ng tr\u1ed1n tr\u00e1nh c\u00f3 th\u1ec3 g\u00e2y l\u1ed7i c\u00fa ph\u00e1p trong c\u00e1c truy v\u1ea5n SQL.<\/li>\n- Vi\u1ebft t\u1eaft:<\/strong> S\u1eed d\u1ee5ng
usr_id<\/code> so v\u1edbi user_id<\/code> so v\u1edbi uid<\/code> trong c\u00e1c b\u1ea3ng kh\u00e1c nhau l\u00e0m gi\u1ea3m \u0111\u1ed9 r\u00f5 r\u00e0ng.<\/li>\n- \u0110\u1ed9 d\u00e0i vs Ng\u1eafn g\u1ecdn:<\/strong> M\u1ed9t s\u1ed1 c\u1ed9t qu\u00e1 d\u00e0i, trong khi nh\u1eefng c\u1ed9t kh\u00e1c l\u00e0 c\u00e1c vi\u1ebft t\u1eaft kh\u00f3 hi\u1ec3u.<\/li>\n<\/ul>\n
Thi\u1ebft l\u1eadp m\u1ed9t Ti\u00eau chu\u1ea9n<\/h3>\n\n- \u00c1p d\u1ee5ng chi\u1ebfn l\u01b0\u1ee3c vi\u1ebft hoa nh\u1ea5t qu\u00e1n (v\u00ed d\u1ee5 nh\u01b0
snake_case<\/code> cho c\u00e1c b\u1ea3ng SQL \u0111\u01b0\u1ee3c khuy\u1ebfn ngh\u1ecb r\u1ed9ng r\u00e3i).<\/li>\n- S\u1eed d\u1ee5ng t\u00ean m\u00f4 t\u1ea3 ph\u1ea3n \u00e1nh \u00fd ngh\u0129a kinh doanh, ch\u1ee9 kh\u00f4ng ph\u1ea3i chi ti\u1ebft tri\u1ec3n khai n\u1ed9i b\u1ed9.<\/li>\n
- Tr\u00e1nh ho\u00e0n to\u00e0n c\u00e1c t\u1eeb kh\u00f3a \u0111\u01b0\u1ee3c b\u1ea3o l\u01b0u. N\u1ebfu kh\u00f4ng th\u1ec3 tr\u00e1nh \u0111\u01b0\u1ee3c, h\u00e3y bao ch\u00fang trong d\u1ea5u ngo\u1eb7c k\u00e9p ho\u1eb7c d\u1ea5u ngo\u1eb7c \u0111\u01a1n ph\u00f9 h\u1ee3p v\u1edbi h\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/li>\n
- Ti\u00eau chu\u1ea9n h\u00f3a t\u00ean b\u1ea3ng s\u1ed1 \u00edt so v\u1edbi s\u1ed1 nhi\u1ec1u. Ch\u1ecdn m\u1ed9t c\u00e1ch v\u00e0 tu\u00e2n theo n\u00f3 (v\u00ed d\u1ee5 nh\u01b0
users<\/code> so v\u1edbi user<\/code>).<\/li>\n- Ti\u1ec1n t\u1ed1 c\u00e1c c\u1ed9t kh\u00f3a ngo\u1ea1i b\u1eb1ng t\u00ean b\u1ea3ng tham chi\u1ebfu (v\u00ed d\u1ee5 nh\u01b0
user_id<\/code>) \u0111\u1ec3 l\u00e0m r\u00f5 m\u1ed1i quan h\u1ec7.<\/li>\n<\/ul>\n6. G\u00e1n c\u1ee9ng gi\u00e1 tr\u1ecb trong l\u01b0\u1ee3c \u0111\u1ed3 \ud83d\uded1<\/h2>\n
C\u00e1c nh\u00e0 thi\u1ebft k\u1ebf \u0111\u00f4i khi nh\u00fang c\u00e1c gi\u00e1 tr\u1ecb kinh doanh c\u1ee5 th\u1ec3 tr\u1ef1c ti\u1ebfp v\u00e0o c\u1ea5u tr\u00fac c\u01a1 s\u1edf d\u1eef li\u1ec7u, ch\u1eb3ng h\u1ea1n nh\u01b0 s\u1eed d\u1ee5ng m\u1ed9t c\u1ed9t \u0111\u1ec3 l\u01b0u m\u00e3 tr\u1ea1ng th\u00e1i c\u1ee5 th\u1ec3 nh\u01b0 active<\/code> ho\u1eb7c inactive<\/code> thay v\u00ec s\u1eed d\u1ee5ng m\u1ed9t tr\u01b0\u1eddng tr\u1ea1ng th\u00e1i chung, ho\u1eb7c m\u00e3 h\u00f3a c\u1ee9ng c\u00e1c lo\u1ea1i ti\u1ec1n t\u1ec7.<\/p>\nT\u00e1c \u0111\u1ed9ng \u0111\u1ebfn t\u00ednh linh ho\u1ea1t<\/h3>\n\n- Thay \u0111\u1ed5i l\u01b0\u1ee3c \u0111\u1ed3:<\/strong> N\u1ebfu c\u1ea7n m\u1ed9t tr\u1ea1ng th\u00e1i m\u1edbi, b\u1ea1n c\u00f3 th\u1ec3 ph\u1ea3i thay \u0111\u1ed5i c\u1ea5u tr\u00fac b\u1ea3ng ho\u1eb7c th\u00eam c\u1ed9t m\u1edbi, d\u1eabn \u0111\u1ebfn th\u1eddi gian ng\u1eebng ho\u1ea1t \u0111\u1ed9ng khi tri\u1ec3n khai.<\/li>\n
- X\u00e1c th\u1ef1c d\u1eef li\u1ec7u:<\/strong> M\u00e3 \u1ee9ng d\u1ee5ng th\u01b0\u1eddng x\u00e1c th\u1ef1c c\u00e1c gi\u00e1 tr\u1ecb n\u00e0y, nh\u01b0ng l\u01b0\u1ee3c \u0111\u1ed3 c\u01a1 s\u1edf d\u1eef li\u1ec7u n\u00ean \u0111\u1ea3m b\u1ea3o c\u00e1c ph\u1ea1m vi ho\u1eb7c t\u1eadp h\u1ee3p h\u1ee3p l\u1ec7 th\u00f4ng qua r\u00e0ng bu\u1ed9c.<\/li>\n
- V\u1ea5n \u0111\u1ec1 \u0111\u1ecba ph\u01b0\u01a1ng h\u00f3a:<\/strong>M\u00e3 h\u00f3a c\u1ee9ng c\u00e1c gi\u00e1 tr\u1ecb v\u0103n b\u1ea3n nh\u01b0
USD<\/code> ho\u1eb7cTi\u1ebfng Anh<\/code> khi\u1ebfn vi\u1ec7c m\u1edf r\u1ed9ng to\u00e0n c\u1ea7u tr\u1edf n\u00ean kh\u00f3 kh\u0103n.<\/li>\n<\/ul>\nT\u00e1i c\u1ea5u tr\u00fac \u0111\u1ec3 m\u1edf r\u1ed9ng quy m\u00f4<\/h3>\n\n- S\u1eed d\u1ee5ngB\u1ea3ng tra c\u1ee9u<\/strong> cho b\u1ea5t k\u1ef3 t\u1eadp h\u1ee3p gi\u00e1 tr\u1ecb n\u00e0o c\u00f3 th\u1ec3 thay \u0111\u1ed5i ho\u1eb7c m\u1edf r\u1ed9ng (v\u00ed d\u1ee5: Tr\u1ea1ng th\u00e1i, Ti\u1ec1n t\u1ec7, Qu\u1ed1c gia).<\/li>\n
- Th\u1ef1c hi\u1ec7nR\u00e0ng bu\u1ed9c ki\u1ec3m tra<\/strong> \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o ch\u1ec9 c\u00f3 c\u00e1c gi\u00e1 tr\u1ecb h\u1ee3p l\u1ec7 \u0111\u01b0\u1ee3c nh\u1eadp, nh\u01b0ng gi\u1eef \u0111\u1ecbnh ngh\u0129a c\u1ee7a c\u00e1c gi\u00e1 tr\u1ecb \u0111\u00f3 trong \u1ee9ng d\u1ee5ng ho\u1eb7c trong m\u1ed9t b\u1ea3ng c\u1ea5u h\u00ecnh ri\u00eang bi\u1ec7t.<\/li>\n
- Ch\u1ec9 s\u1eed d\u1ee5ng ki\u1ec3u Enum n\u1ebfu h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u h\u1ed7 tr\u1ee3 ch\u00fang m\u1ed9t c\u00e1ch v\u1eefng ch\u1eafc v\u00e0 t\u1eadp h\u1ee3p gi\u00e1 tr\u1ecb th\u1ef1c s\u1ef1 c\u1ed1 \u0111\u1ecbnh.<\/li>\n
- T\u00e1ch d\u1eef li\u1ec7u c\u1ea5u h\u00ecnh kh\u1ecfi d\u1eef li\u1ec7u giao d\u1ecbch.<\/li>\n<\/ul>\n
7. B\u1ecf qua kh\u1ea3 n\u0103ng m\u1edf r\u1ed9ng trong t\u01b0\u01a1ng lai \ud83d\udcc8<\/h2>\n
Nhi\u1ec1u s\u01a1 \u0111\u1ed3 ERD \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf cho k\u00edch th\u01b0\u1edbc t\u1eadp d\u1eef li\u1ec7u hi\u1ec7n t\u1ea1i m\u00e0 kh\u00f4ng t\u00ednh \u0111\u1ebfn s\u1ef1 ph\u00e1t tri\u1ec3n. M\u1ed9t l\u01b0\u1ee3c \u0111\u1ed3 ho\u1ea1t \u0111\u1ed9ng t\u1ed1t v\u1edbi 1.000 b\u1ea3n ghi c\u00f3 th\u1ec3 th\u1ea5t b\u1ea1i nghi\u00eam tr\u1ecdng khi \u0111\u1ea1t \u0111\u1ebfn 10 tri\u1ec7u b\u1ea3n ghi do c\u00e1c v\u1ea5n \u0111\u1ec1 v\u1ec1 kh\u00f3a, ch\u1ec9 m\u1ee5c ho\u1eb7c chia t\u00e1ch d\u1eef li\u1ec7u.<\/p>\n
Nh\u1eefng sai l\u1ea7m v\u1ec1 kh\u1ea3 n\u0103ng m\u1edf r\u1ed9ng<\/h3>\n\n- C\u00e1c tr\u01b0\u1eddng v\u0103n b\u1ea3n l\u1edbn:<\/strong>L\u01b0u tr\u1eef c\u00e1c kh\u1ed1i d\u1eef li\u1ec7u l\u1edbn ho\u1eb7c chu\u1ed7i v\u0103n b\u1ea3n d\u00e0i trong b\u1ea3ng ch\u00ednh c\u00f3 th\u1ec3 l\u00e0m t\u0103ng k\u00edch th\u01b0\u1edbc ch\u1ec9 m\u1ee5c v\u00e0 l\u00e0m ch\u1eadm thao t\u00e1c \u0111\u1ecdc.<\/li>\n
- Thi\u1ebfu kh\u00f3a chia t\u00e1ch d\u1eef li\u1ec7u:<\/strong> N\u1ebfu l\u01b0\u1ee3c \u0111\u1ed3 kh\u00f4ng t\u00ednh \u0111\u1ebfn c\u00e1ch d\u1eef li\u1ec7u s\u1ebd \u0111\u01b0\u1ee3c chia nh\u1ecf ho\u1eb7c ph\u00e2n v\u00f9ng (v\u00ed d\u1ee5: theo ng\u00e0y ho\u1eb7c khu v\u1ef1c), vi\u1ec7c m\u1edf r\u1ed9ng ngang trong t\u01b0\u01a1ng lai s\u1ebd tr\u1edf th\u00e0nh m\u1ed9t thay \u0111\u1ed5i l\u1edbn.<\/li>\n
- Thi\u1ebfu ch\u1ec9 m\u1ee5c:<\/strong> Kh\u00f4ng l\u01b0\u1eddng tr\u01b0\u1edbc \u0111\u01b0\u1ee3c c\u00e1c c\u1ed9t n\u00e0o s\u1ebd \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 l\u1ecdc ho\u1eb7c s\u1eafp x\u1ebfp trong t\u01b0\u01a1ng lai d\u1eabn \u0111\u1ebfn c\u00e1c \u0111i\u1ec3m ngh\u1ebdn hi\u1ec7u su\u1ea5t.<\/li>\n
- M\u1eabu vi\u1ebft nhi\u1ec1u:<\/strong>M\u1ed9t thi\u1ebft k\u1ebf \u0111\u01b0\u1ee3c t\u1ed1i \u01b0u h\u00f3a cho thao t\u00e1c \u0111\u1ecdc c\u00f3 th\u1ec3 b\u1ecb ngh\u1ebdn khi th\u1ef1c hi\u1ec7n vi\u1ebft v\u1edbi kh\u1ed1i l\u01b0\u1ee3ng l\u1edbn do c\u01a1 ch\u1ebf kh\u00f3a tr\u00ean c\u00e1c kh\u00f3a ngo\u1ea1i.<\/li>\n<\/ul>\n
Thi\u1ebft k\u1ebf \u0111\u1ec3 ph\u00e1t tri\u1ec3n<\/h3>\n\n- Xem l\u1ea1i T\u1ef7 l\u1ec7 \u0111\u1ecdc\/vi\u1ebft<\/strong> c\u1ee7a \u1ee9ng d\u1ee5ng c\u1ee7a b\u1ea1n. N\u1ebfu n\u00f3 c\u00f3 xu h\u01b0\u1edbng vi\u1ebft nhi\u1ec1u, h\u00e3y t\u1ed1i thi\u1ec3u h\u00f3a c\u00e1c r\u00e0ng bu\u1ed9c kh\u00f3a ngo\u1ea1i g\u00e2y ra hi\u1ec7n t\u01b0\u1ee3ng kh\u00f3a.<\/li>\n
- Thi\u1ebft k\u1ebf Kh\u00f3a ph\u00e2n v\u00f9ng<\/strong> v\u00e0o s\u01a1 \u0111\u1ed3 ch\u00ednh c\u1ee7a b\u1ea1n. \u0110\u1ea3m b\u1ea3o m\u1ecdi b\u1ea3ng \u0111\u1ec1u c\u00f3 m\u1ed9t c\u1ed9t c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 chia d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch h\u1ee3p l\u00fd.<\/li>\n
- T\u00e1ch d\u1eef li\u1ec7u v\u0103n b\u1ea3n l\u1edbn v\u00e0o m\u1ed9t b\u1ea3ng ri\u00eang bi\u1ec7t (m\u1ed1i quan h\u1ec7 1:1) \u0111\u1ec3 gi\u1eef cho ch\u1ec9 m\u1ee5c ch\u00ednh lu\u00f4n g\u1ecdn nh\u1eb9.<\/li>\n
- L\u00ean k\u1ebf ho\u1ea1ch cho X\u00f3a m\u1ec1m<\/strong> thay v\u00ec x\u00f3a c\u1ee9ng \u0111\u1ec3 b\u1ea3o t\u1ed3n l\u1ecbch s\u1eed d\u1eef li\u1ec7u m\u00e0 kh\u00f4ng \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn hi\u1ec7u su\u1ea5t truy v\u1ea5n hi\u1ec7n t\u1ea1i.<\/li>\n<\/ul>\n
T\u00f3m t\u1eaft c\u00e1c th\u1ef1c h\u00e0nh t\u1ed1t nh\u1ea5t \ud83d\udccb<\/h2>\n
\u0110\u1ec3 \u0111\u1ea3m b\u1ea3o c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n lu\u00f4n \u1ed5n \u0111\u1ecbnh v\u00e0 d\u1ec5 b\u1ea3o tr\u00ec, h\u00e3y xem x\u00e9t s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 c\u1ee7a b\u1ea1n theo danh s\u00e1ch ki\u1ec3m tra sau tr\u01b0\u1edbc khi tri\u1ec3n khai.<\/p>\n
\n- Kh\u00f3a:<\/strong> M\u1ed7i b\u1ea3ng \u0111\u1ec1u c\u00f3 kh\u00f3a ch\u00ednh. C\u00e1c kh\u00f3a ngo\u1ea1i \u0111\u01b0\u1ee3c l\u1eadp ch\u1ec9 m\u1ee5c.<\/li>\n
- M\u1ed1i quan h\u1ec7:<\/strong> T\u00ednh cardinality \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh r\u00f5 r\u00e0ng. M\u1ed1i quan h\u1ec7 nhi\u1ec1u-nhi\u1ec1u s\u1eed d\u1ee5ng b\u1ea3ng li\u00ean k\u1ebft.<\/li>\n
- Chu\u1ea9n h\u00f3a:<\/strong> S\u1ef1 tr\u00f9ng l\u1eb7p d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c gi\u1ea3m thi\u1ec3u theo ti\u00eau chu\u1ea9n 3NF.<\/li>\n
- Ph\u1ee5 thu\u1ed9c:<\/strong> Kh\u00f4ng c\u00f3 v\u00f2ng l\u1eb7p kh\u00f3a ngo\u1ea1i v\u00f2ng m\u00e0 kh\u00f4ng c\u00f3 r\u00e0ng bu\u1ed9c ho\u00e3n l\u1ea1i.<\/li>\n
- \u0110\u1eb7t t\u00ean:<\/strong> S\u1eed d\u1ee5ng c\u00e1ch vi\u1ebft hoa nh\u1ea5t qu\u00e1n v\u00e0 t\u00ean m\u00f4 t\u1ea3 tr\u00ean to\u00e0n b\u1ed9 h\u1ec7 th\u1ed1ng.<\/li>\n
- Gi\u00e1 tr\u1ecb:<\/strong> Kh\u00f4ng c\u00f3 logic kinh doanh \u0111\u01b0\u1ee3c ghi c\u1ee9ng trong c\u1ea5u tr\u00fac l\u01b0\u1ee3c \u0111\u1ed3.<\/li>\n
- M\u1edf r\u1ed9ng:<\/strong> L\u01b0\u1ee3c \u0111\u1ed3 xem x\u00e9t c\u00e1c chi\u1ebfn l\u01b0\u1ee3c ph\u00e2n v\u00f9ng v\u00e0 l\u1eadp ch\u1ec9 m\u1ee5c \u0111\u1ec3 x\u1eed l\u00fd t\u1ea3i trong t\u01b0\u01a1ng lai.<\/li>\n<\/ul>\n
Suy ngh\u0129 cu\u1ed1i c\u00f9ng v\u1ec1 m\u00f4 h\u00ecnh h\u00f3a d\u1eef li\u1ec7u \ud83e\udde0<\/h2>\n
X\u00e2y d\u1ef1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u kh\u00f4ng ch\u1ec9 \u0111\u01a1n thu\u1ea7n l\u00e0 vi\u1ebftCREATE TABLE<\/code> c\u00e1c c\u00e2u l\u1ec7nh. \u0110\u00f3 l\u00e0 vi\u1ec7c m\u00f4 h\u00ecnh h\u00f3a th\u1ef1c t\u1ebf c\u1ee7a c\u00e1c quy tr\u00ecnh kinh doanh c\u1ee7a b\u1ea1n th\u00e0nh m\u1ed9t c\u1ea5u tr\u00fac logic m\u00e0 m\u00e1y t\u00ednh c\u00f3 th\u1ec3 x\u1eed l\u00fd m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3. Chi ph\u00ed s\u1eeda l\u1ed7i l\u01b0\u1ee3c \u0111\u1ed3 t\u0103ng theo c\u1ea5p s\u1ed1 nh\u00e2n n\u1ebfu ph\u00e1t hi\u1ec7n l\u1ed7i c\u00e0ng mu\u1ed9n trong chu k\u1ef3 ph\u00e1t tri\u1ec3n.<\/p>\nB\u1eb1ng c\u00e1ch tr\u00e1nh b\u1ea3y sai l\u1ea7m ph\u1ed5 bi\u1ebfn n\u00e0y, b\u1ea1n s\u1ebd gi\u1ea3m n\u1ee3 k\u1ef9 thu\u1eadt v\u00e0 t\u1ea1o n\u1ec1n t\u1ea3ng h\u1ed7 tr\u1ee3 c\u00e1c truy v\u1ea5n ph\u1ee9c t\u1ea1p v\u00e0 giao d\u1ecbch kh\u1ed1i l\u01b0\u1ee3ng l\u1edbn. H\u00e3y \u01b0u ti\u00ean s\u1ef1 r\u00f5 r\u00e0ng, t\u00ednh to\u00e0n v\u1eb9n v\u00e0 t\u00ednh linh ho\u1ea1t trong s\u01a1 \u0111\u1ed3 c\u1ee7a b\u1ea1n. M\u1ed9t s\u01a1 \u0111\u1ed3 ERD \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf t\u1ed1t s\u1ebd v\u00f4 h\u00ecnh v\u1edbi ng\u01b0\u1eddi d\u00f9ng cu\u1ed1i nh\u01b0ng l\u1ea1i thi\u1ebft y\u1ebfu cho s\u1ef1 b\u1ec1n v\u1eefng c\u1ee7a h\u1ec7 th\u1ed1ng.<\/p>\n
D\u00e0nh th\u1eddi gian xem x\u00e9t l\u1ea1i l\u01b0\u1ee3c \u0111\u1ed3 c\u1ee7a b\u1ea1n v\u1edbi c\u00e1i nh\u00ecn m\u1edbi m\u1ebb ho\u1eb7c th\u00f4ng qua quy tr\u00ecnh ki\u1ec3m tra b\u1edfi \u0111\u1ed3ng nghi\u1ec7p. \u0110\u1eb7t c\u00e2u h\u1ecfi v\u1ec1 l\u00fd do t\u1ea1i sao m\u1ed9t m\u1ed1i quan h\u1ec7 t\u1ed3n t\u1ea1i v\u00e0 n\u00f3 s\u1ebd ho\u1ea1t \u0111\u1ed9ng th\u1ebf n\u00e0o khi ch\u1ecbu t\u1ea3i. S\u1ef1 c\u1ea9n tr\u1ecdng n\u00e0y s\u1ebd mang l\u1ea1i l\u1ee3i \u00edch cho \u0111\u1ed9 tin c\u1eady c\u1ee7a h\u1ec7 th\u1ed1ng v\u00e0 n\u0103ng su\u1ea5t ph\u00e1t tri\u1ec3n c\u1ee7a nh\u00e0 ph\u00e1t tri\u1ec3n trong t\u01b0\u01a1ng lai.<\/p>\n","protected":false},"excerpt":{"rendered":"
Thi\u1ebft k\u1ebf m\u1ed9t c\u1ea5u tr\u00fac d\u1eef li\u1ec7u v\u1eefng ch\u1eafc l\u00e0 n\u1ec1n t\u1ea3ng c\u1ee7a b\u1ea5t k\u1ef3 h\u1ec7 th\u1ed1ng ph\u1ea7n m\u1ec1m \u0111\u00e1ng tin c\u1eady n\u00e0o. S\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 (ERD)…<\/p>\n","protected":false},"author":1,"featured_media":1604,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_yoast_wpseo_title":"7 Sai l\u1ea7m trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 khi\u1ebfn c\u01a1 s\u1edf d\u1eef li\u1ec7u b\u1ecb h\u1ecfng (v\u00e0 c\u00e1ch tr\u00e1nh ch\u00fang) \ud83d\udee0\ufe0f","_yoast_wpseo_metadesc":"Kh\u00e1m ph\u00e1 nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 l\u00e0m \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u. H\u1ecdc c\u00e1ch thi\u1ebft k\u1ebf c\u00e1c l\u01b0\u1ee3c \u0111\u1ed3 v\u1eefng ch\u1eafc v\u00e0 tr\u00e1nh vi\u1ec7c t\u00e1i c\u1ea5u tr\u00fac t\u1ed1n k\u00e9m.","fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[88],"tags":[84,87],"class_list":["post-1603","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-erd","tag-academic","tag-erd"],"yoast_head":"\n
7 Sai l\u1ea7m trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 khi\u1ebfn c\u01a1 s\u1edf d\u1eef li\u1ec7u b\u1ecb h\u1ecfng (v\u00e0 c\u00e1ch tr\u00e1nh ch\u00fang) \ud83d\udee0\ufe0f<\/title>\n<meta name=\"description\" content=\"Kh\u00e1m ph\u00e1 nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 l\u00e0m \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u. H\u1ecdc c\u00e1ch thi\u1ebft k\u1ebf c\u00e1c l\u01b0\u1ee3c \u0111\u1ed3 v\u1eefng ch\u1eafc v\u00e0 tr\u00e1nh vi\u1ec7c t\u00e1i c\u1ea5u tr\u00fac t\u1ed1n k\u00e9m.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.viz-read.com\/vi\/7-erd-mistakes-break-databases-avoid\/\" \/>\n<meta property=\"og:locale\" content=\"vi_VN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"7 Sai l\u1ea7m trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 khi\u1ebfn c\u01a1 s\u1edf d\u1eef li\u1ec7u b\u1ecb h\u1ecfng (v\u00e0 c\u00e1ch tr\u00e1nh ch\u00fang) \ud83d\udee0\ufe0f\" \/>\n<meta property=\"og:description\" content=\"Kh\u00e1m ph\u00e1 nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 l\u00e0m \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u. 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H\u1ecdc c\u00e1ch thi\u1ebft k\u1ebf c\u00e1c l\u01b0\u1ee3c \u0111\u1ed3 v\u1eefng ch\u1eafc v\u00e0 tr\u00e1nh vi\u1ec7c t\u00e1i c\u1ea5u tr\u00fac t\u1ed1n k\u00e9m.","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.viz-read.com\/vi\/7-erd-mistakes-break-databases-avoid\/","og_locale":"vi_VN","og_type":"article","og_title":"7 Sai l\u1ea7m trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 khi\u1ebfn c\u01a1 s\u1edf d\u1eef li\u1ec7u b\u1ecb h\u1ecfng (v\u00e0 c\u00e1ch tr\u00e1nh ch\u00fang) \ud83d\udee0\ufe0f","og_description":"Kh\u00e1m ph\u00e1 nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 l\u00e0m \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u. 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Th\u1ef1c h\u00e0nh T\u1ed1t \u0111\u1ec3 Tr\u00e1nh L\u1ed7i N\u00e0y<\/h3>\n\n- Lu\u00f4n \u0111\u1ecbnh ngh\u0129a kh\u00f3a ch\u00ednh cho m\u1ecdi b\u1ea3ng, ngay c\u1ea3 khi n\u00f3 c\u00f3 v\u1ebb th\u1eeba.<\/li>\n
- \u01afu ti\u00ean s\u1eed d\u1ee5ng kh\u00f3a gi\u1ea3 (s\u1ed1 nguy\u00ean t\u1ef1 t\u0103ng ho\u1eb7c UUID) thay v\u00ec kh\u00f3a t\u1ef1 nhi\u00ean (nh\u01b0 \u0111\u1ecba ch\u1ec9 email ho\u1eb7c s\u1ed1 \u0111i\u1ec7n tho\u1ea1i) \u0111\u1ec3 tr\u00e1nh vi\u1ec7c thay \u0111\u1ed5i logic kinh doanh \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn l\u01b0\u1ee3c \u0111\u1ed3.<\/li>\n
- \u0110\u1ea3m b\u1ea3o c\u1ed9t kh\u00f3a ch\u00ednh kh\u00f4ng \u0111\u01b0\u1ee3c ph\u00e9p null.<\/li>\n
- Ch\u1ec9 s\u1eed d\u1ee5ng kh\u00f3a h\u1ee3p th\u00e0nh khi m\u1ed9t c\u1ed9t duy nh\u1ea5t kh\u00f4ng th\u1ec3 x\u00e1c \u0111\u1ecbnh duy nh\u1ea5t m\u1ed9t h\u00e0ng, v\u00ed d\u1ee5 nh\u01b0 trong c\u00e1c b\u1ea3ng quan h\u1ec7 nhi\u1ec1u-nhi\u1ec1u.<\/li>\n<\/ul>\n
2. Cardinality M\u1ed1i quan h\u1ec7 M\u1eadp m\u1edd \ud83d\udd04<\/h2>\n
Cardinality x\u00e1c \u0111\u1ecbnh m\u1ed1i quan h\u1ec7 s\u1ed1 l\u01b0\u1ee3ng gi\u1eefa c\u00e1c b\u1ea3n ghi trong hai b\u1ea3ng. C\u00e1c lo\u1ea1i ph\u1ed5 bi\u1ebfn bao g\u1ed3m m\u1ed9t-\u0111\u1ed1i-m\u1ed9t, m\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u v\u00e0 nhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u. Bi\u1ec3u di\u1ec5n sai c\u00e1c m\u1ed1i quan h\u1ec7 n\u00e0y trong s\u01a1 \u0111\u1ed3 s\u1ebd d\u1eabn \u0111\u1ebfn s\u1ef1 kh\u00f4ng kh\u1edbp c\u1ea5u tr\u00fac trong c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u1eadt l\u00fd.<\/p>\n
Nh\u1eefng Sai L\u1ea7m Ph\u1ed5 Bi\u1ebfn<\/h3>\n\n- Gi\u1ea3 \u0111\u1ecbnh M\u1ed9t-\u0110\u1ed1i-Nhi\u1ec1u:<\/strong>C\u00e1c nh\u00e0 thi\u1ebft k\u1ebf th\u01b0\u1eddng m\u1eb7c \u0111\u1ecbnh m\u1ed1i quan h\u1ec7 m\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u khi th\u1ef1c t\u1ebf l\u00e0 nhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u. V\u00ed d\u1ee5, m\u1ed9t sinh vi\u00ean c\u00f3 th\u1ec3 \u0111\u0103ng k\u00fd nhi\u1ec1u kh\u00f3a h\u1ecdc, v\u00e0 m\u1ed9t kh\u00f3a h\u1ecdc c\u00f3 th\u1ec3 c\u00f3 nhi\u1ec1u sinh vi\u00ean. M\u00f4 h\u00ecnh h\u00f3a \u0111i\u1ec1u n\u00e0y d\u01b0\u1edbi d\u1ea1ng m\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u s\u1ebd y\u00eau c\u1ea7u sao ch\u00e9p d\u1eef li\u1ec7u sinh vi\u00ean tr\u00ean nhi\u1ec1u h\u00e0ng kh\u00f3a h\u1ecdc.<\/li>\n
- C\u00e1c \u0111\u01b0\u1eddng n\u1ed1i Kh\u00f4ng Nh\u00e3n:<\/strong>C\u00e1c \u0111\u01b0\u1eddng n\u1ed1i trong ERD n\u00ean th\u1ec3 hi\u1ec7n cardinality (v\u00ed d\u1ee5 nh\u01b0 k\u00fd hi\u1ec7u ch\u00e2n chim). B\u1ecf tr\u1ed1ng nh\u00e3n s\u1ebd khi\u1ebfn c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n ph\u1ea3i \u0111o\u00e1n c\u00e1ch d\u1eef li\u1ec7u li\u00ean h\u1ec7 v\u1edbi nhau.<\/li>\n
- B\u1ecf qua Kh\u1ea3 n\u0103ng Null:<\/strong>M\u1ed1i quan h\u1ec7 m\u1ed9t-\u0111\u1ed1i-m\u1ed9t c\u00f3 th\u1ec3 cho ph\u00e9p c\u00e1c gi\u00e1 tr\u1ecb null trong c\u1ed9t kh\u00f3a ngo\u1ea1i n\u1ebfu m\u1ed1i quan h\u1ec7 l\u00e0 t\u00f9y ch\u1ecdn. Kh\u00f4ng m\u00f4 h\u00ecnh h\u00f3a r\u00e0ng bu\u1ed9c n\u00e0y s\u1ebd cho ph\u00e9p t\u1ed3n t\u1ea1i c\u00e1c b\u1ea3n ghi b\u1ecb b\u1ecf r\u01a1i.<\/li>\n<\/ul>\n
C\u00e1ch Ti\u1ebfp C\u1eadn \u0110\u00fang<\/h3>\n\n- M\u00f4 h\u00ecnh h\u00f3a r\u00f5 r\u00e0ng c\u00e1c m\u1ed1i quan h\u1ec7 nhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng b\u1ea3ng giao nhau (b\u1ea3ng li\u00ean k\u1ebft) ch\u1ee9a c\u00e1c kh\u00f3a ngo\u1ea1i t\u1eeb c\u1ea3 hai b\u1ea3ng li\u00ean quan.<\/li>\n
- Ghi r\u00f5 cardinality tr\u00ean c\u00e1c \u0111\u01b0\u1eddng n\u1ed1i trong s\u01a1 \u0111\u1ed3.<\/li>\n
- \u00c1p d\u1ee5ng c\u00e1c r\u00e0ng bu\u1ed9c c\u01a1 s\u1edf d\u1eef li\u1ec7u (nh\u01b0 r\u00e0ng bu\u1ed9c UNIQUE tr\u00ean kh\u00f3a ngo\u1ea1i) \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o logic trong s\u01a1 \u0111\u1ed3 \u0111\u01b0\u1ee3c th\u1ef1c thi.<\/li>\n<\/ul>\n
\n\n\nLo\u1ea1i quan h\u1ec7<\/th>\n Chi\u1ebfn l\u01b0\u1ee3c tri\u1ec3n khai<\/th>\n L\u1ed7i ph\u1ed5 bi\u1ebfn<\/th>\n<\/tr>\n<\/thead>\n \n\nM\u1ed9t-\u0111\u1ed1i-m\u1ed9t<\/td>\n Kh\u00f3a ngo\u1ea1i trong m\u1ed9t b\u1ea3ng v\u1edbi r\u00e0ng bu\u1ed9c UNIQUE<\/td>\n Th\u00eam kh\u00f3a ngo\u1ea1i v\u00e0o c\u1ea3 hai b\u1ea3ng m\u1ed9t c\u00e1ch kh\u00f4ng c\u1ea7n thi\u1ebft<\/td>\n<\/tr>\n \nM\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u<\/td>\n Kh\u00f3a ngo\u1ea1i trong b\u1ea3ng \u201cNhi\u1ec1u\u201d<\/td>\n L\u01b0u tr\u1eef d\u1eef li\u1ec7u cha trong b\u1ea3ng con (phi chu\u1ea9n h\u00f3a)<\/td>\n<\/tr>\n \nNhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u<\/td>\n B\u1ea3ng li\u00ean k\u1ebft trung gian<\/td>\n L\u01b0u tr\u1eef nhi\u1ec1u ID trong m\u1ed9t c\u1ed9t ph\u00e2n c\u00e1ch b\u1eb1ng d\u1ea5u ph\u1ea9y<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n3. B\u1ecf qua c\u00e1c ti\u00eau chu\u1ea9n chu\u1ea9n h\u00f3a \ud83d\udcc9<\/h2>\n
Chu\u1ea9n h\u00f3a l\u00e0 qu\u00e1 tr\u00ecnh t\u1ed5 ch\u1ee9c d\u1eef li\u1ec7u nh\u1eb1m gi\u1ea3m thi\u1ec3u s\u1ef1 tr\u00f9ng l\u1eb7p v\u00e0 c\u1ea3i thi\u1ec7n t\u00ednh to\u00e0n v\u1eb9n. Trong khi m\u1ed9t s\u1ed1 h\u1ec7 th\u1ed1ng hi\u1ec7n \u0111\u1ea1i ch\u1ea5p nh\u1eadn phi chu\u1ea9n h\u00f3a \u0111\u1ec3 t\u0103ng hi\u1ec7u su\u1ea5t \u0111\u1ecdc, nh\u01b0ng b\u1ecf qua ho\u00e0n to\u00e0n chu\u1ea9n h\u00f3a trong giai \u0111o\u1ea1n thi\u1ebft k\u1ebf s\u1ebd t\u1ea1o ra g\u00e1nh n\u1eb7ng b\u1ea3o tr\u00ec \u0111\u00e1ng k\u1ec3.<\/p>\n
R\u1ee7i ro c\u1ee7a vi\u1ec7c chu\u1ea9n h\u00f3a k\u00e9m<\/h3>\n\n- L\u1ed7i c\u1eadp nh\u1eadt:<\/strong> N\u1ebfu \u0111\u1ecba ch\u1ec9 kh\u00e1ch h\u00e0ng \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef trong n\u0103m b\u1ea3ng \u0111\u01a1n h\u00e0ng kh\u00e1c nhau, vi\u1ec7c c\u1eadp nh\u1eadt \u0111\u1ecba ch\u1ec9 c\u1ee7a h\u1ecd \u0111\u00f2i h\u1ecfi n\u0103m thao t\u00e1c c\u1eadp nh\u1eadt ri\u00eang bi\u1ec7t. N\u1ebfu m\u1ed9t thao t\u00e1c th\u1ea5t b\u1ea1i, d\u1eef li\u1ec7u s\u1ebd tr\u1edf n\u00ean kh\u00f4ng nh\u1ea5t qu\u00e1n.<\/li>\n
- L\u1ed7i ch\u00e8n:<\/strong> B\u1ea1n c\u00f3 th\u1ec3 kh\u00f4ng th\u1ec3 th\u00eam m\u1ed9t danh m\u1ee5c s\u1ea3n ph\u1ea9m m\u1edbi m\u00e0 kh\u00f4ng c\u1ea7n th\u00eam b\u1ea3n ghi s\u1ea3n ph\u1ea9m, bu\u1ed9c ph\u1ea3i t\u1ea1o d\u1eef li\u1ec7u gi\u1ea3.<\/li>\n
- L\u1ed7i x\u00f3a:<\/strong> Vi\u1ec7c x\u00f3a m\u1ed9t b\u1ea3n ghi c\u00f3 th\u1ec3 v\u00f4 t\u00ecnh lo\u1ea1i b\u1ecf d\u1eef li\u1ec7u quan tr\u1ecdng li\u00ean quan \u0111\u1ebfn c\u00e1c th\u1ef1c th\u1ec3 kh\u00e1c.<\/li>\n<\/ul>\n
H\u01b0\u1edbng d\u1eabn tri\u1ec3n khai<\/h3>\n\n- M\u1ee5c ti\u00eau h\u01b0\u1edbng t\u1edbi d\u1ea1ng chu\u1ea9n h\u00f3a th\u1ee9 ba (3NF) nh\u01b0 m\u1ed9t n\u1ec1n t\u1ea3ng. \u0110i\u1ec1u n\u00e0y \u0111\u1ea3m b\u1ea3o r\u1eb1ng c\u00e1c c\u1ed9t ch\u1ec9 ph\u1ee5 thu\u1ed9c v\u00e0o kh\u00f3a ch\u00ednh.<\/li>\n
- X\u00e1c \u0111\u1ecbnh c\u00e1c ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u n\u01a1i m\u1ed9t c\u1ed9t kh\u00f4ng ph\u1ea3i kh\u00f3a ph\u1ee5 thu\u1ed9c v\u00e0o m\u1ed9t c\u1ed9t kh\u00f4ng ph\u1ea3i kh\u00f3a kh\u00e1c.<\/li>\n
- T\u00e1ch bi\u1ec7t c\u00e1c th\u1ef1c th\u1ec3 ri\u00eang bi\u1ec7t. N\u1ebfu m\u1ed9t b\u1ea3ng ch\u1ee9a th\u00f4ng tin v\u1ec1 c\u1ea3 \u201c\u0110\u01a1n h\u00e0ng\u201d v\u00e0 \u201cKh\u00e1ch h\u00e0ng\u201d, h\u00e3y t\u00e1ch ch\u00fang ra.<\/li>\n
- Ch\u1ec9 phi chu\u1ea9n h\u00f3a sau khi ph\u00e2n t\u00edch hi\u1ec7u su\u1ea5t truy v\u1ea5n. \u0110\u1eebng t\u1ed1i \u01b0u h\u00f3a tr\u01b0\u1edbc cho t\u1ed1c \u0111\u1ed9 m\u00e0 \u0111\u00e1nh \u0111\u1ed5i t\u00ednh to\u00e0n v\u1eb9n.<\/li>\n<\/ul>\n
4. T\u1ea1o ra c\u00e1c ph\u1ee5 thu\u1ed9c v\u00f2ng l\u1eb7p \ud83d\udd01<\/h2>\n
C\u00e1c ph\u1ee5 thu\u1ed9c v\u00f2ng x\u1ea3y ra khi c\u00e1c b\u1ea3ng tham chi\u1ebfu l\u1eabn nhau theo m\u1ed9t v\u00f2ng l\u1eb7p, ng\u0103n c\u1ea3n qu\u00e1 tr\u00ecnh kh\u1edfi t\u1ea1o ho\u1eb7c g\u00e2y ra \u0111\u1ec7 quy v\u00f4 h\u1ea1n trong truy v\u1ea5n. M\u1eb7c d\u00f9 c\u00e1c m\u1ed1i quan h\u1ec7 \u0111\u1ec7 quy (nh\u01b0 s\u01a1 \u0111\u1ed3 t\u1ed5 ch\u1ee9c n\u01a1i m\u1ed9t nh\u00e2n vi\u00ean c\u00f3 ng\u01b0\u1eddi qu\u1ea3n l\u00fd) l\u00e0 h\u1ee3p l\u1ec7, nh\u01b0ng c\u00e1c kh\u00f3a ngo\u1ea1i v\u00f2ng l\u1eb7p kh\u00f4ng ki\u1ec3m so\u00e1t \u0111\u01b0\u1ee3c c\u00f3 th\u1ec3 l\u00e0m h\u1ecfng c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/p>\n
T\u1ea1i sao \u0111i\u1ec1u n\u00e0y l\u00e0m h\u1ecfng h\u1ec7 th\u1ed1ng<\/h3>\n\n- L\u1ed7i kh\u1edfi t\u1ea1o:<\/strong> Trong qu\u00e1 tr\u00ecnh tri\u1ec3n khai, b\u1ed9 \u0111\u1ed9ng c\u01a1 c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u00f3 th\u1ec3 t\u1eeb ch\u1ed1i vi\u1ec7c t\u1ea1o r\u00e0ng bu\u1ed9c kh\u00f3a ngo\u1ea1i n\u1ebfu t\u1ed3n t\u1ea1i tham chi\u1ebfu v\u00f2ng l\u1eb7p (v\u00ed d\u1ee5: B\u1ea3ng A tham chi\u1ebfu B, v\u00e0 B tham chi\u1ebfu A) tr\u1eeb khi \u0111\u01b0\u1ee3c x\u1eed l\u00fd b\u1eb1ng c\u00e1c r\u00e0ng bu\u1ed9c ho\u00e3n l\u1ea1i.<\/li>\n
- Tr\u00e0n ng\u0103n x\u1ebfp truy v\u1ea5n:<\/strong>C\u00e1c truy v\u1ea5n \u0111\u1ec7 quy \u0111i qua nh\u1eefng v\u00f2ng l\u1eb7p n\u00e0y m\u00e0 kh\u00f4ng c\u00f3 \u0111i\u1ec1u ki\u1ec7n d\u1eebng c\u00f3 th\u1ec3 ti\u00eau th\u1ee5 to\u00e0n b\u1ed9 b\u1ed9 nh\u1edb s\u1eb5n c\u00f3.<\/li>\n
- Vi ph\u1ea1m t\u00ednh to\u00e0n v\u1eb9n tham chi\u1ebfu:<\/strong>X\u00f3a b\u1ea3ng cha c\u00f3 th\u1ec3 th\u1ea5t b\u1ea1i n\u1ebfu c\u00e1c b\u1ea3ng con ch\u01b0a \u0111\u01b0\u1ee3c d\u1ecdn d\u1eb9p, nh\u01b0ng vi\u1ec7c d\u1ecdn d\u1eb9p c\u00e1c b\u1ea3ng con c\u0169ng c\u00f3 th\u1ec3 th\u1ea5t b\u1ea1i do c\u00e1c ph\u1ee5 thu\u1ed9c kh\u00e1c.<\/li>\n<\/ul>\n
C\u00e1ch kh\u1eafc ph\u1ee5c<\/h3>\n\n- S\u1eed d\u1ee5ng R\u00e0ng bu\u1ed9c ho\u00e3n l\u1ea1i<\/strong> n\u1ebfu c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n h\u1ed7 tr\u1ee3 ch\u00fang, cho ph\u00e9p c\u01a1 s\u1edf d\u1eef li\u1ec7u ki\u1ec3m tra c\u00e1c m\u1ed1i quan h\u1ec7 sau khi t\u1ea5t c\u1ea3 d\u1eef li\u1ec7u \u0111\u00e3 \u0111\u01b0\u1ee3c t\u1ea3i.<\/li>\n
- \u0110\u1ed1i v\u1edbi c\u00e1c b\u1ea3ng tham chi\u1ebfu t\u1ef1 th\u00e2n (nh\u01b0 danh m\u1ee5c), \u0111\u1ea3m b\u1ea3o kh\u00f3a ngo\u1ea1i c\u00f3 th\u1ec3 \u0111\u1ec3 tr\u1ed1ng \u0111\u1ec3 cho ph\u00e9p c\u00e1c n\u00fat g\u1ed1c.<\/li>\n
- Thi\u1ebft k\u1ebf l\u01b0\u1ee3c \u0111\u1ed3 \u0111\u1ec3 cho ph\u00e9p m\u1ed9t c\u1ea5u tr\u00fac ph\u00e2n c\u1ea5p logic m\u00e0 kh\u00f4ng bu\u1ed9c ph\u1ea3i c\u00f3 v\u00f2ng l\u1eb7p kh\u00f3a ngo\u1ea1i v\u1eadt l\u00fd \u1edf m\u1ecdi c\u1ea5p \u0111\u1ed9.<\/li>\n
- Th\u1ef1c hi\u1ec7n x\u00f3a m\u1ec1m \u0111\u1ec3 qu\u1ea3n l\u00fd c\u00e1c thao t\u00e1c x\u00f3a lan truy\u1ec1n m\u1ed9t c\u00e1ch an to\u00e0n.<\/li>\n<\/ul>\n
5. Quy \u01b0\u1edbc \u0111\u1eb7t t\u00ean kh\u00f4ng nh\u1ea5t qu\u00e1n \ud83d\udcdd<\/h2>\n
T\u00ean l\u00e0 giao di\u1ec7n gi\u1eefa con ng\u01b0\u1eddi v\u00e0 m\u00e1y m\u00f3c. Vi\u1ec7c \u0111\u1eb7t t\u00ean kh\u00f4ng nh\u1ea5t qu\u00e1n trong t\u00ean b\u1ea3ng v\u00e0 c\u1ed9t khi\u1ebfn l\u01b0\u1ee3c \u0111\u1ed3 tr\u1edf n\u00ean kh\u00f3 hi\u1ec3u, kh\u00f3 b\u1ea3o tr\u00ec v\u00e0 truy v\u1ea5n. \u0110i\u1ec1u n\u00e0y th\u01b0\u1eddng xu\u1ea5t ph\u00e1t t\u1eeb vi\u1ec7c thi\u1ebfu m\u1ed9t h\u01b0\u1edbng d\u1eabn phong c\u00e1ch chung.<\/p>\n
C\u00e1c v\u1ea5n \u0111\u1ec1 c\u1ee5 th\u1ec3<\/h3>\n\n- Nhi\u1ec1u ch\u1eef hoa v\u00e0 th\u01b0\u1eddng:<\/strong>Pha tr\u1ed9n
camelCase<\/code>, snake_case<\/code>, v\u00e0 PascalCase<\/code> khi\u1ebfn c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n khi truy v\u1ea5n d\u1eef li\u1ec7u b\u1ecb nh\u1ea7m l\u1eabn.<\/li>\n- T\u1eeb kh\u00f3a \u0111\u01b0\u1ee3c b\u1ea3o l\u01b0u:<\/strong> S\u1eed d\u1ee5ng t\u00ean nh\u01b0
order<\/code>, group<\/code>, ho\u1eb7c user<\/code> m\u00e0 kh\u00f4ng tr\u1ed1n tr\u00e1nh c\u00f3 th\u1ec3 g\u00e2y l\u1ed7i c\u00fa ph\u00e1p trong c\u00e1c truy v\u1ea5n SQL.<\/li>\n- Vi\u1ebft t\u1eaft:<\/strong> S\u1eed d\u1ee5ng
usr_id<\/code> so v\u1edbi user_id<\/code> so v\u1edbi uid<\/code> trong c\u00e1c b\u1ea3ng kh\u00e1c nhau l\u00e0m gi\u1ea3m \u0111\u1ed9 r\u00f5 r\u00e0ng.<\/li>\n- \u0110\u1ed9 d\u00e0i vs Ng\u1eafn g\u1ecdn:<\/strong> M\u1ed9t s\u1ed1 c\u1ed9t qu\u00e1 d\u00e0i, trong khi nh\u1eefng c\u1ed9t kh\u00e1c l\u00e0 c\u00e1c vi\u1ebft t\u1eaft kh\u00f3 hi\u1ec3u.<\/li>\n<\/ul>\n
Thi\u1ebft l\u1eadp m\u1ed9t Ti\u00eau chu\u1ea9n<\/h3>\n\n- \u00c1p d\u1ee5ng chi\u1ebfn l\u01b0\u1ee3c vi\u1ebft hoa nh\u1ea5t qu\u00e1n (v\u00ed d\u1ee5 nh\u01b0
snake_case<\/code> cho c\u00e1c b\u1ea3ng SQL \u0111\u01b0\u1ee3c khuy\u1ebfn ngh\u1ecb r\u1ed9ng r\u00e3i).<\/li>\n- S\u1eed d\u1ee5ng t\u00ean m\u00f4 t\u1ea3 ph\u1ea3n \u00e1nh \u00fd ngh\u0129a kinh doanh, ch\u1ee9 kh\u00f4ng ph\u1ea3i chi ti\u1ebft tri\u1ec3n khai n\u1ed9i b\u1ed9.<\/li>\n
- Tr\u00e1nh ho\u00e0n to\u00e0n c\u00e1c t\u1eeb kh\u00f3a \u0111\u01b0\u1ee3c b\u1ea3o l\u01b0u. N\u1ebfu kh\u00f4ng th\u1ec3 tr\u00e1nh \u0111\u01b0\u1ee3c, h\u00e3y bao ch\u00fang trong d\u1ea5u ngo\u1eb7c k\u00e9p ho\u1eb7c d\u1ea5u ngo\u1eb7c \u0111\u01a1n ph\u00f9 h\u1ee3p v\u1edbi h\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/li>\n
- Ti\u00eau chu\u1ea9n h\u00f3a t\u00ean b\u1ea3ng s\u1ed1 \u00edt so v\u1edbi s\u1ed1 nhi\u1ec1u. Ch\u1ecdn m\u1ed9t c\u00e1ch v\u00e0 tu\u00e2n theo n\u00f3 (v\u00ed d\u1ee5 nh\u01b0
users<\/code> so v\u1edbi user<\/code>).<\/li>\n- Ti\u1ec1n t\u1ed1 c\u00e1c c\u1ed9t kh\u00f3a ngo\u1ea1i b\u1eb1ng t\u00ean b\u1ea3ng tham chi\u1ebfu (v\u00ed d\u1ee5 nh\u01b0
user_id<\/code>) \u0111\u1ec3 l\u00e0m r\u00f5 m\u1ed1i quan h\u1ec7.<\/li>\n<\/ul>\n6. G\u00e1n c\u1ee9ng gi\u00e1 tr\u1ecb trong l\u01b0\u1ee3c \u0111\u1ed3 \ud83d\uded1<\/h2>\n
C\u00e1c nh\u00e0 thi\u1ebft k\u1ebf \u0111\u00f4i khi nh\u00fang c\u00e1c gi\u00e1 tr\u1ecb kinh doanh c\u1ee5 th\u1ec3 tr\u1ef1c ti\u1ebfp v\u00e0o c\u1ea5u tr\u00fac c\u01a1 s\u1edf d\u1eef li\u1ec7u, ch\u1eb3ng h\u1ea1n nh\u01b0 s\u1eed d\u1ee5ng m\u1ed9t c\u1ed9t \u0111\u1ec3 l\u01b0u m\u00e3 tr\u1ea1ng th\u00e1i c\u1ee5 th\u1ec3 nh\u01b0 active<\/code> ho\u1eb7c inactive<\/code> thay v\u00ec s\u1eed d\u1ee5ng m\u1ed9t tr\u01b0\u1eddng tr\u1ea1ng th\u00e1i chung, ho\u1eb7c m\u00e3 h\u00f3a c\u1ee9ng c\u00e1c lo\u1ea1i ti\u1ec1n t\u1ec7.<\/p>\nT\u00e1c \u0111\u1ed9ng \u0111\u1ebfn t\u00ednh linh ho\u1ea1t<\/h3>\n\n- Thay \u0111\u1ed5i l\u01b0\u1ee3c \u0111\u1ed3:<\/strong> N\u1ebfu c\u1ea7n m\u1ed9t tr\u1ea1ng th\u00e1i m\u1edbi, b\u1ea1n c\u00f3 th\u1ec3 ph\u1ea3i thay \u0111\u1ed5i c\u1ea5u tr\u00fac b\u1ea3ng ho\u1eb7c th\u00eam c\u1ed9t m\u1edbi, d\u1eabn \u0111\u1ebfn th\u1eddi gian ng\u1eebng ho\u1ea1t \u0111\u1ed9ng khi tri\u1ec3n khai.<\/li>\n
- X\u00e1c th\u1ef1c d\u1eef li\u1ec7u:<\/strong> M\u00e3 \u1ee9ng d\u1ee5ng th\u01b0\u1eddng x\u00e1c th\u1ef1c c\u00e1c gi\u00e1 tr\u1ecb n\u00e0y, nh\u01b0ng l\u01b0\u1ee3c \u0111\u1ed3 c\u01a1 s\u1edf d\u1eef li\u1ec7u n\u00ean \u0111\u1ea3m b\u1ea3o c\u00e1c ph\u1ea1m vi ho\u1eb7c t\u1eadp h\u1ee3p h\u1ee3p l\u1ec7 th\u00f4ng qua r\u00e0ng bu\u1ed9c.<\/li>\n
- V\u1ea5n \u0111\u1ec1 \u0111\u1ecba ph\u01b0\u01a1ng h\u00f3a:<\/strong>M\u00e3 h\u00f3a c\u1ee9ng c\u00e1c gi\u00e1 tr\u1ecb v\u0103n b\u1ea3n nh\u01b0
USD<\/code> ho\u1eb7cTi\u1ebfng Anh<\/code> khi\u1ebfn vi\u1ec7c m\u1edf r\u1ed9ng to\u00e0n c\u1ea7u tr\u1edf n\u00ean kh\u00f3 kh\u0103n.<\/li>\n<\/ul>\nT\u00e1i c\u1ea5u tr\u00fac \u0111\u1ec3 m\u1edf r\u1ed9ng quy m\u00f4<\/h3>\n\n- S\u1eed d\u1ee5ngB\u1ea3ng tra c\u1ee9u<\/strong> cho b\u1ea5t k\u1ef3 t\u1eadp h\u1ee3p gi\u00e1 tr\u1ecb n\u00e0o c\u00f3 th\u1ec3 thay \u0111\u1ed5i ho\u1eb7c m\u1edf r\u1ed9ng (v\u00ed d\u1ee5: Tr\u1ea1ng th\u00e1i, Ti\u1ec1n t\u1ec7, Qu\u1ed1c gia).<\/li>\n
- Th\u1ef1c hi\u1ec7nR\u00e0ng bu\u1ed9c ki\u1ec3m tra<\/strong> \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o ch\u1ec9 c\u00f3 c\u00e1c gi\u00e1 tr\u1ecb h\u1ee3p l\u1ec7 \u0111\u01b0\u1ee3c nh\u1eadp, nh\u01b0ng gi\u1eef \u0111\u1ecbnh ngh\u0129a c\u1ee7a c\u00e1c gi\u00e1 tr\u1ecb \u0111\u00f3 trong \u1ee9ng d\u1ee5ng ho\u1eb7c trong m\u1ed9t b\u1ea3ng c\u1ea5u h\u00ecnh ri\u00eang bi\u1ec7t.<\/li>\n
- Ch\u1ec9 s\u1eed d\u1ee5ng ki\u1ec3u Enum n\u1ebfu h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u h\u1ed7 tr\u1ee3 ch\u00fang m\u1ed9t c\u00e1ch v\u1eefng ch\u1eafc v\u00e0 t\u1eadp h\u1ee3p gi\u00e1 tr\u1ecb th\u1ef1c s\u1ef1 c\u1ed1 \u0111\u1ecbnh.<\/li>\n
- T\u00e1ch d\u1eef li\u1ec7u c\u1ea5u h\u00ecnh kh\u1ecfi d\u1eef li\u1ec7u giao d\u1ecbch.<\/li>\n<\/ul>\n
7. B\u1ecf qua kh\u1ea3 n\u0103ng m\u1edf r\u1ed9ng trong t\u01b0\u01a1ng lai \ud83d\udcc8<\/h2>\n
Nhi\u1ec1u s\u01a1 \u0111\u1ed3 ERD \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf cho k\u00edch th\u01b0\u1edbc t\u1eadp d\u1eef li\u1ec7u hi\u1ec7n t\u1ea1i m\u00e0 kh\u00f4ng t\u00ednh \u0111\u1ebfn s\u1ef1 ph\u00e1t tri\u1ec3n. M\u1ed9t l\u01b0\u1ee3c \u0111\u1ed3 ho\u1ea1t \u0111\u1ed9ng t\u1ed1t v\u1edbi 1.000 b\u1ea3n ghi c\u00f3 th\u1ec3 th\u1ea5t b\u1ea1i nghi\u00eam tr\u1ecdng khi \u0111\u1ea1t \u0111\u1ebfn 10 tri\u1ec7u b\u1ea3n ghi do c\u00e1c v\u1ea5n \u0111\u1ec1 v\u1ec1 kh\u00f3a, ch\u1ec9 m\u1ee5c ho\u1eb7c chia t\u00e1ch d\u1eef li\u1ec7u.<\/p>\n
Nh\u1eefng sai l\u1ea7m v\u1ec1 kh\u1ea3 n\u0103ng m\u1edf r\u1ed9ng<\/h3>\n\n- C\u00e1c tr\u01b0\u1eddng v\u0103n b\u1ea3n l\u1edbn:<\/strong>L\u01b0u tr\u1eef c\u00e1c kh\u1ed1i d\u1eef li\u1ec7u l\u1edbn ho\u1eb7c chu\u1ed7i v\u0103n b\u1ea3n d\u00e0i trong b\u1ea3ng ch\u00ednh c\u00f3 th\u1ec3 l\u00e0m t\u0103ng k\u00edch th\u01b0\u1edbc ch\u1ec9 m\u1ee5c v\u00e0 l\u00e0m ch\u1eadm thao t\u00e1c \u0111\u1ecdc.<\/li>\n
- Thi\u1ebfu kh\u00f3a chia t\u00e1ch d\u1eef li\u1ec7u:<\/strong> N\u1ebfu l\u01b0\u1ee3c \u0111\u1ed3 kh\u00f4ng t\u00ednh \u0111\u1ebfn c\u00e1ch d\u1eef li\u1ec7u s\u1ebd \u0111\u01b0\u1ee3c chia nh\u1ecf ho\u1eb7c ph\u00e2n v\u00f9ng (v\u00ed d\u1ee5: theo ng\u00e0y ho\u1eb7c khu v\u1ef1c), vi\u1ec7c m\u1edf r\u1ed9ng ngang trong t\u01b0\u01a1ng lai s\u1ebd tr\u1edf th\u00e0nh m\u1ed9t thay \u0111\u1ed5i l\u1edbn.<\/li>\n
- Thi\u1ebfu ch\u1ec9 m\u1ee5c:<\/strong> Kh\u00f4ng l\u01b0\u1eddng tr\u01b0\u1edbc \u0111\u01b0\u1ee3c c\u00e1c c\u1ed9t n\u00e0o s\u1ebd \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 l\u1ecdc ho\u1eb7c s\u1eafp x\u1ebfp trong t\u01b0\u01a1ng lai d\u1eabn \u0111\u1ebfn c\u00e1c \u0111i\u1ec3m ngh\u1ebdn hi\u1ec7u su\u1ea5t.<\/li>\n
- M\u1eabu vi\u1ebft nhi\u1ec1u:<\/strong>M\u1ed9t thi\u1ebft k\u1ebf \u0111\u01b0\u1ee3c t\u1ed1i \u01b0u h\u00f3a cho thao t\u00e1c \u0111\u1ecdc c\u00f3 th\u1ec3 b\u1ecb ngh\u1ebdn khi th\u1ef1c hi\u1ec7n vi\u1ebft v\u1edbi kh\u1ed1i l\u01b0\u1ee3ng l\u1edbn do c\u01a1 ch\u1ebf kh\u00f3a tr\u00ean c\u00e1c kh\u00f3a ngo\u1ea1i.<\/li>\n<\/ul>\n
Thi\u1ebft k\u1ebf \u0111\u1ec3 ph\u00e1t tri\u1ec3n<\/h3>\n\n- Xem l\u1ea1i T\u1ef7 l\u1ec7 \u0111\u1ecdc\/vi\u1ebft<\/strong> c\u1ee7a \u1ee9ng d\u1ee5ng c\u1ee7a b\u1ea1n. N\u1ebfu n\u00f3 c\u00f3 xu h\u01b0\u1edbng vi\u1ebft nhi\u1ec1u, h\u00e3y t\u1ed1i thi\u1ec3u h\u00f3a c\u00e1c r\u00e0ng bu\u1ed9c kh\u00f3a ngo\u1ea1i g\u00e2y ra hi\u1ec7n t\u01b0\u1ee3ng kh\u00f3a.<\/li>\n
- Thi\u1ebft k\u1ebf Kh\u00f3a ph\u00e2n v\u00f9ng<\/strong> v\u00e0o s\u01a1 \u0111\u1ed3 ch\u00ednh c\u1ee7a b\u1ea1n. \u0110\u1ea3m b\u1ea3o m\u1ecdi b\u1ea3ng \u0111\u1ec1u c\u00f3 m\u1ed9t c\u1ed9t c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 chia d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch h\u1ee3p l\u00fd.<\/li>\n
- T\u00e1ch d\u1eef li\u1ec7u v\u0103n b\u1ea3n l\u1edbn v\u00e0o m\u1ed9t b\u1ea3ng ri\u00eang bi\u1ec7t (m\u1ed1i quan h\u1ec7 1:1) \u0111\u1ec3 gi\u1eef cho ch\u1ec9 m\u1ee5c ch\u00ednh lu\u00f4n g\u1ecdn nh\u1eb9.<\/li>\n
- L\u00ean k\u1ebf ho\u1ea1ch cho X\u00f3a m\u1ec1m<\/strong> thay v\u00ec x\u00f3a c\u1ee9ng \u0111\u1ec3 b\u1ea3o t\u1ed3n l\u1ecbch s\u1eed d\u1eef li\u1ec7u m\u00e0 kh\u00f4ng \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn hi\u1ec7u su\u1ea5t truy v\u1ea5n hi\u1ec7n t\u1ea1i.<\/li>\n<\/ul>\n
T\u00f3m t\u1eaft c\u00e1c th\u1ef1c h\u00e0nh t\u1ed1t nh\u1ea5t \ud83d\udccb<\/h2>\n
\u0110\u1ec3 \u0111\u1ea3m b\u1ea3o c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n lu\u00f4n \u1ed5n \u0111\u1ecbnh v\u00e0 d\u1ec5 b\u1ea3o tr\u00ec, h\u00e3y xem x\u00e9t s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 c\u1ee7a b\u1ea1n theo danh s\u00e1ch ki\u1ec3m tra sau tr\u01b0\u1edbc khi tri\u1ec3n khai.<\/p>\n
\n- Kh\u00f3a:<\/strong> M\u1ed7i b\u1ea3ng \u0111\u1ec1u c\u00f3 kh\u00f3a ch\u00ednh. C\u00e1c kh\u00f3a ngo\u1ea1i \u0111\u01b0\u1ee3c l\u1eadp ch\u1ec9 m\u1ee5c.<\/li>\n
- M\u1ed1i quan h\u1ec7:<\/strong> T\u00ednh cardinality \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh r\u00f5 r\u00e0ng. M\u1ed1i quan h\u1ec7 nhi\u1ec1u-nhi\u1ec1u s\u1eed d\u1ee5ng b\u1ea3ng li\u00ean k\u1ebft.<\/li>\n
- Chu\u1ea9n h\u00f3a:<\/strong> S\u1ef1 tr\u00f9ng l\u1eb7p d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c gi\u1ea3m thi\u1ec3u theo ti\u00eau chu\u1ea9n 3NF.<\/li>\n
- Ph\u1ee5 thu\u1ed9c:<\/strong> Kh\u00f4ng c\u00f3 v\u00f2ng l\u1eb7p kh\u00f3a ngo\u1ea1i v\u00f2ng m\u00e0 kh\u00f4ng c\u00f3 r\u00e0ng bu\u1ed9c ho\u00e3n l\u1ea1i.<\/li>\n
- \u0110\u1eb7t t\u00ean:<\/strong> S\u1eed d\u1ee5ng c\u00e1ch vi\u1ebft hoa nh\u1ea5t qu\u00e1n v\u00e0 t\u00ean m\u00f4 t\u1ea3 tr\u00ean to\u00e0n b\u1ed9 h\u1ec7 th\u1ed1ng.<\/li>\n
- Gi\u00e1 tr\u1ecb:<\/strong> Kh\u00f4ng c\u00f3 logic kinh doanh \u0111\u01b0\u1ee3c ghi c\u1ee9ng trong c\u1ea5u tr\u00fac l\u01b0\u1ee3c \u0111\u1ed3.<\/li>\n
- M\u1edf r\u1ed9ng:<\/strong> L\u01b0\u1ee3c \u0111\u1ed3 xem x\u00e9t c\u00e1c chi\u1ebfn l\u01b0\u1ee3c ph\u00e2n v\u00f9ng v\u00e0 l\u1eadp ch\u1ec9 m\u1ee5c \u0111\u1ec3 x\u1eed l\u00fd t\u1ea3i trong t\u01b0\u01a1ng lai.<\/li>\n<\/ul>\n
Suy ngh\u0129 cu\u1ed1i c\u00f9ng v\u1ec1 m\u00f4 h\u00ecnh h\u00f3a d\u1eef li\u1ec7u \ud83e\udde0<\/h2>\n
X\u00e2y d\u1ef1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u kh\u00f4ng ch\u1ec9 \u0111\u01a1n thu\u1ea7n l\u00e0 vi\u1ebftCREATE TABLE<\/code> c\u00e1c c\u00e2u l\u1ec7nh. \u0110\u00f3 l\u00e0 vi\u1ec7c m\u00f4 h\u00ecnh h\u00f3a th\u1ef1c t\u1ebf c\u1ee7a c\u00e1c quy tr\u00ecnh kinh doanh c\u1ee7a b\u1ea1n th\u00e0nh m\u1ed9t c\u1ea5u tr\u00fac logic m\u00e0 m\u00e1y t\u00ednh c\u00f3 th\u1ec3 x\u1eed l\u00fd m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3. Chi ph\u00ed s\u1eeda l\u1ed7i l\u01b0\u1ee3c \u0111\u1ed3 t\u0103ng theo c\u1ea5p s\u1ed1 nh\u00e2n n\u1ebfu ph\u00e1t hi\u1ec7n l\u1ed7i c\u00e0ng mu\u1ed9n trong chu k\u1ef3 ph\u00e1t tri\u1ec3n.<\/p>\nB\u1eb1ng c\u00e1ch tr\u00e1nh b\u1ea3y sai l\u1ea7m ph\u1ed5 bi\u1ebfn n\u00e0y, b\u1ea1n s\u1ebd gi\u1ea3m n\u1ee3 k\u1ef9 thu\u1eadt v\u00e0 t\u1ea1o n\u1ec1n t\u1ea3ng h\u1ed7 tr\u1ee3 c\u00e1c truy v\u1ea5n ph\u1ee9c t\u1ea1p v\u00e0 giao d\u1ecbch kh\u1ed1i l\u01b0\u1ee3ng l\u1edbn. H\u00e3y \u01b0u ti\u00ean s\u1ef1 r\u00f5 r\u00e0ng, t\u00ednh to\u00e0n v\u1eb9n v\u00e0 t\u00ednh linh ho\u1ea1t trong s\u01a1 \u0111\u1ed3 c\u1ee7a b\u1ea1n. M\u1ed9t s\u01a1 \u0111\u1ed3 ERD \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf t\u1ed1t s\u1ebd v\u00f4 h\u00ecnh v\u1edbi ng\u01b0\u1eddi d\u00f9ng cu\u1ed1i nh\u01b0ng l\u1ea1i thi\u1ebft y\u1ebfu cho s\u1ef1 b\u1ec1n v\u1eefng c\u1ee7a h\u1ec7 th\u1ed1ng.<\/p>\n
D\u00e0nh th\u1eddi gian xem x\u00e9t l\u1ea1i l\u01b0\u1ee3c \u0111\u1ed3 c\u1ee7a b\u1ea1n v\u1edbi c\u00e1i nh\u00ecn m\u1edbi m\u1ebb ho\u1eb7c th\u00f4ng qua quy tr\u00ecnh ki\u1ec3m tra b\u1edfi \u0111\u1ed3ng nghi\u1ec7p. \u0110\u1eb7t c\u00e2u h\u1ecfi v\u1ec1 l\u00fd do t\u1ea1i sao m\u1ed9t m\u1ed1i quan h\u1ec7 t\u1ed3n t\u1ea1i v\u00e0 n\u00f3 s\u1ebd ho\u1ea1t \u0111\u1ed9ng th\u1ebf n\u00e0o khi ch\u1ecbu t\u1ea3i. S\u1ef1 c\u1ea9n tr\u1ecdng n\u00e0y s\u1ebd mang l\u1ea1i l\u1ee3i \u00edch cho \u0111\u1ed9 tin c\u1eady c\u1ee7a h\u1ec7 th\u1ed1ng v\u00e0 n\u0103ng su\u1ea5t ph\u00e1t tri\u1ec3n c\u1ee7a nh\u00e0 ph\u00e1t tri\u1ec3n trong t\u01b0\u01a1ng lai.<\/p>\n","protected":false},"excerpt":{"rendered":"
Thi\u1ebft k\u1ebf m\u1ed9t c\u1ea5u tr\u00fac d\u1eef li\u1ec7u v\u1eefng ch\u1eafc l\u00e0 n\u1ec1n t\u1ea3ng c\u1ee7a b\u1ea5t k\u1ef3 h\u1ec7 th\u1ed1ng ph\u1ea7n m\u1ec1m \u0111\u00e1ng tin c\u1eady n\u00e0o. S\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 (ERD)…<\/p>\n","protected":false},"author":1,"featured_media":1604,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_yoast_wpseo_title":"7 Sai l\u1ea7m trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 khi\u1ebfn c\u01a1 s\u1edf d\u1eef li\u1ec7u b\u1ecb h\u1ecfng (v\u00e0 c\u00e1ch tr\u00e1nh ch\u00fang) \ud83d\udee0\ufe0f","_yoast_wpseo_metadesc":"Kh\u00e1m ph\u00e1 nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 l\u00e0m \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u. H\u1ecdc c\u00e1ch thi\u1ebft k\u1ebf c\u00e1c l\u01b0\u1ee3c \u0111\u1ed3 v\u1eefng ch\u1eafc v\u00e0 tr\u00e1nh vi\u1ec7c t\u00e1i c\u1ea5u tr\u00fac t\u1ed1n k\u00e9m.","fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[88],"tags":[84,87],"class_list":["post-1603","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-erd","tag-academic","tag-erd"],"yoast_head":"\n
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2. Cardinality M\u1ed1i quan h\u1ec7 M\u1eadp m\u1edd \ud83d\udd04<\/h2>\n
Cardinality x\u00e1c \u0111\u1ecbnh m\u1ed1i quan h\u1ec7 s\u1ed1 l\u01b0\u1ee3ng gi\u1eefa c\u00e1c b\u1ea3n ghi trong hai b\u1ea3ng. C\u00e1c lo\u1ea1i ph\u1ed5 bi\u1ebfn bao g\u1ed3m m\u1ed9t-\u0111\u1ed1i-m\u1ed9t, m\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u v\u00e0 nhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u. Bi\u1ec3u di\u1ec5n sai c\u00e1c m\u1ed1i quan h\u1ec7 n\u00e0y trong s\u01a1 \u0111\u1ed3 s\u1ebd d\u1eabn \u0111\u1ebfn s\u1ef1 kh\u00f4ng kh\u1edbp c\u1ea5u tr\u00fac trong c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u1eadt l\u00fd.<\/p>\n
Nh\u1eefng Sai L\u1ea7m Ph\u1ed5 Bi\u1ebfn<\/h3>\n\n- Gi\u1ea3 \u0111\u1ecbnh M\u1ed9t-\u0110\u1ed1i-Nhi\u1ec1u:<\/strong>C\u00e1c nh\u00e0 thi\u1ebft k\u1ebf th\u01b0\u1eddng m\u1eb7c \u0111\u1ecbnh m\u1ed1i quan h\u1ec7 m\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u khi th\u1ef1c t\u1ebf l\u00e0 nhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u. V\u00ed d\u1ee5, m\u1ed9t sinh vi\u00ean c\u00f3 th\u1ec3 \u0111\u0103ng k\u00fd nhi\u1ec1u kh\u00f3a h\u1ecdc, v\u00e0 m\u1ed9t kh\u00f3a h\u1ecdc c\u00f3 th\u1ec3 c\u00f3 nhi\u1ec1u sinh vi\u00ean. M\u00f4 h\u00ecnh h\u00f3a \u0111i\u1ec1u n\u00e0y d\u01b0\u1edbi d\u1ea1ng m\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u s\u1ebd y\u00eau c\u1ea7u sao ch\u00e9p d\u1eef li\u1ec7u sinh vi\u00ean tr\u00ean nhi\u1ec1u h\u00e0ng kh\u00f3a h\u1ecdc.<\/li>\n
- C\u00e1c \u0111\u01b0\u1eddng n\u1ed1i Kh\u00f4ng Nh\u00e3n:<\/strong>C\u00e1c \u0111\u01b0\u1eddng n\u1ed1i trong ERD n\u00ean th\u1ec3 hi\u1ec7n cardinality (v\u00ed d\u1ee5 nh\u01b0 k\u00fd hi\u1ec7u ch\u00e2n chim). B\u1ecf tr\u1ed1ng nh\u00e3n s\u1ebd khi\u1ebfn c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n ph\u1ea3i \u0111o\u00e1n c\u00e1ch d\u1eef li\u1ec7u li\u00ean h\u1ec7 v\u1edbi nhau.<\/li>\n
- B\u1ecf qua Kh\u1ea3 n\u0103ng Null:<\/strong>M\u1ed1i quan h\u1ec7 m\u1ed9t-\u0111\u1ed1i-m\u1ed9t c\u00f3 th\u1ec3 cho ph\u00e9p c\u00e1c gi\u00e1 tr\u1ecb null trong c\u1ed9t kh\u00f3a ngo\u1ea1i n\u1ebfu m\u1ed1i quan h\u1ec7 l\u00e0 t\u00f9y ch\u1ecdn. Kh\u00f4ng m\u00f4 h\u00ecnh h\u00f3a r\u00e0ng bu\u1ed9c n\u00e0y s\u1ebd cho ph\u00e9p t\u1ed3n t\u1ea1i c\u00e1c b\u1ea3n ghi b\u1ecb b\u1ecf r\u01a1i.<\/li>\n<\/ul>\n
C\u00e1ch Ti\u1ebfp C\u1eadn \u0110\u00fang<\/h3>\n\n- M\u00f4 h\u00ecnh h\u00f3a r\u00f5 r\u00e0ng c\u00e1c m\u1ed1i quan h\u1ec7 nhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng b\u1ea3ng giao nhau (b\u1ea3ng li\u00ean k\u1ebft) ch\u1ee9a c\u00e1c kh\u00f3a ngo\u1ea1i t\u1eeb c\u1ea3 hai b\u1ea3ng li\u00ean quan.<\/li>\n
- Ghi r\u00f5 cardinality tr\u00ean c\u00e1c \u0111\u01b0\u1eddng n\u1ed1i trong s\u01a1 \u0111\u1ed3.<\/li>\n
- \u00c1p d\u1ee5ng c\u00e1c r\u00e0ng bu\u1ed9c c\u01a1 s\u1edf d\u1eef li\u1ec7u (nh\u01b0 r\u00e0ng bu\u1ed9c UNIQUE tr\u00ean kh\u00f3a ngo\u1ea1i) \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o logic trong s\u01a1 \u0111\u1ed3 \u0111\u01b0\u1ee3c th\u1ef1c thi.<\/li>\n<\/ul>\n
\n\n\nLo\u1ea1i quan h\u1ec7<\/th>\n Chi\u1ebfn l\u01b0\u1ee3c tri\u1ec3n khai<\/th>\n L\u1ed7i ph\u1ed5 bi\u1ebfn<\/th>\n<\/tr>\n<\/thead>\n \n\nM\u1ed9t-\u0111\u1ed1i-m\u1ed9t<\/td>\n Kh\u00f3a ngo\u1ea1i trong m\u1ed9t b\u1ea3ng v\u1edbi r\u00e0ng bu\u1ed9c UNIQUE<\/td>\n Th\u00eam kh\u00f3a ngo\u1ea1i v\u00e0o c\u1ea3 hai b\u1ea3ng m\u1ed9t c\u00e1ch kh\u00f4ng c\u1ea7n thi\u1ebft<\/td>\n<\/tr>\n \nM\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u<\/td>\n Kh\u00f3a ngo\u1ea1i trong b\u1ea3ng \u201cNhi\u1ec1u\u201d<\/td>\n L\u01b0u tr\u1eef d\u1eef li\u1ec7u cha trong b\u1ea3ng con (phi chu\u1ea9n h\u00f3a)<\/td>\n<\/tr>\n \nNhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u<\/td>\n B\u1ea3ng li\u00ean k\u1ebft trung gian<\/td>\n L\u01b0u tr\u1eef nhi\u1ec1u ID trong m\u1ed9t c\u1ed9t ph\u00e2n c\u00e1ch b\u1eb1ng d\u1ea5u ph\u1ea9y<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n3. B\u1ecf qua c\u00e1c ti\u00eau chu\u1ea9n chu\u1ea9n h\u00f3a \ud83d\udcc9<\/h2>\n
Chu\u1ea9n h\u00f3a l\u00e0 qu\u00e1 tr\u00ecnh t\u1ed5 ch\u1ee9c d\u1eef li\u1ec7u nh\u1eb1m gi\u1ea3m thi\u1ec3u s\u1ef1 tr\u00f9ng l\u1eb7p v\u00e0 c\u1ea3i thi\u1ec7n t\u00ednh to\u00e0n v\u1eb9n. Trong khi m\u1ed9t s\u1ed1 h\u1ec7 th\u1ed1ng hi\u1ec7n \u0111\u1ea1i ch\u1ea5p nh\u1eadn phi chu\u1ea9n h\u00f3a \u0111\u1ec3 t\u0103ng hi\u1ec7u su\u1ea5t \u0111\u1ecdc, nh\u01b0ng b\u1ecf qua ho\u00e0n to\u00e0n chu\u1ea9n h\u00f3a trong giai \u0111o\u1ea1n thi\u1ebft k\u1ebf s\u1ebd t\u1ea1o ra g\u00e1nh n\u1eb7ng b\u1ea3o tr\u00ec \u0111\u00e1ng k\u1ec3.<\/p>\n
R\u1ee7i ro c\u1ee7a vi\u1ec7c chu\u1ea9n h\u00f3a k\u00e9m<\/h3>\n\n- L\u1ed7i c\u1eadp nh\u1eadt:<\/strong> N\u1ebfu \u0111\u1ecba ch\u1ec9 kh\u00e1ch h\u00e0ng \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef trong n\u0103m b\u1ea3ng \u0111\u01a1n h\u00e0ng kh\u00e1c nhau, vi\u1ec7c c\u1eadp nh\u1eadt \u0111\u1ecba ch\u1ec9 c\u1ee7a h\u1ecd \u0111\u00f2i h\u1ecfi n\u0103m thao t\u00e1c c\u1eadp nh\u1eadt ri\u00eang bi\u1ec7t. N\u1ebfu m\u1ed9t thao t\u00e1c th\u1ea5t b\u1ea1i, d\u1eef li\u1ec7u s\u1ebd tr\u1edf n\u00ean kh\u00f4ng nh\u1ea5t qu\u00e1n.<\/li>\n
- L\u1ed7i ch\u00e8n:<\/strong> B\u1ea1n c\u00f3 th\u1ec3 kh\u00f4ng th\u1ec3 th\u00eam m\u1ed9t danh m\u1ee5c s\u1ea3n ph\u1ea9m m\u1edbi m\u00e0 kh\u00f4ng c\u1ea7n th\u00eam b\u1ea3n ghi s\u1ea3n ph\u1ea9m, bu\u1ed9c ph\u1ea3i t\u1ea1o d\u1eef li\u1ec7u gi\u1ea3.<\/li>\n
- L\u1ed7i x\u00f3a:<\/strong> Vi\u1ec7c x\u00f3a m\u1ed9t b\u1ea3n ghi c\u00f3 th\u1ec3 v\u00f4 t\u00ecnh lo\u1ea1i b\u1ecf d\u1eef li\u1ec7u quan tr\u1ecdng li\u00ean quan \u0111\u1ebfn c\u00e1c th\u1ef1c th\u1ec3 kh\u00e1c.<\/li>\n<\/ul>\n
H\u01b0\u1edbng d\u1eabn tri\u1ec3n khai<\/h3>\n\n- M\u1ee5c ti\u00eau h\u01b0\u1edbng t\u1edbi d\u1ea1ng chu\u1ea9n h\u00f3a th\u1ee9 ba (3NF) nh\u01b0 m\u1ed9t n\u1ec1n t\u1ea3ng. \u0110i\u1ec1u n\u00e0y \u0111\u1ea3m b\u1ea3o r\u1eb1ng c\u00e1c c\u1ed9t ch\u1ec9 ph\u1ee5 thu\u1ed9c v\u00e0o kh\u00f3a ch\u00ednh.<\/li>\n
- X\u00e1c \u0111\u1ecbnh c\u00e1c ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u n\u01a1i m\u1ed9t c\u1ed9t kh\u00f4ng ph\u1ea3i kh\u00f3a ph\u1ee5 thu\u1ed9c v\u00e0o m\u1ed9t c\u1ed9t kh\u00f4ng ph\u1ea3i kh\u00f3a kh\u00e1c.<\/li>\n
- T\u00e1ch bi\u1ec7t c\u00e1c th\u1ef1c th\u1ec3 ri\u00eang bi\u1ec7t. N\u1ebfu m\u1ed9t b\u1ea3ng ch\u1ee9a th\u00f4ng tin v\u1ec1 c\u1ea3 \u201c\u0110\u01a1n h\u00e0ng\u201d v\u00e0 \u201cKh\u00e1ch h\u00e0ng\u201d, h\u00e3y t\u00e1ch ch\u00fang ra.<\/li>\n
- Ch\u1ec9 phi chu\u1ea9n h\u00f3a sau khi ph\u00e2n t\u00edch hi\u1ec7u su\u1ea5t truy v\u1ea5n. \u0110\u1eebng t\u1ed1i \u01b0u h\u00f3a tr\u01b0\u1edbc cho t\u1ed1c \u0111\u1ed9 m\u00e0 \u0111\u00e1nh \u0111\u1ed5i t\u00ednh to\u00e0n v\u1eb9n.<\/li>\n<\/ul>\n
4. T\u1ea1o ra c\u00e1c ph\u1ee5 thu\u1ed9c v\u00f2ng l\u1eb7p \ud83d\udd01<\/h2>\n
C\u00e1c ph\u1ee5 thu\u1ed9c v\u00f2ng x\u1ea3y ra khi c\u00e1c b\u1ea3ng tham chi\u1ebfu l\u1eabn nhau theo m\u1ed9t v\u00f2ng l\u1eb7p, ng\u0103n c\u1ea3n qu\u00e1 tr\u00ecnh kh\u1edfi t\u1ea1o ho\u1eb7c g\u00e2y ra \u0111\u1ec7 quy v\u00f4 h\u1ea1n trong truy v\u1ea5n. M\u1eb7c d\u00f9 c\u00e1c m\u1ed1i quan h\u1ec7 \u0111\u1ec7 quy (nh\u01b0 s\u01a1 \u0111\u1ed3 t\u1ed5 ch\u1ee9c n\u01a1i m\u1ed9t nh\u00e2n vi\u00ean c\u00f3 ng\u01b0\u1eddi qu\u1ea3n l\u00fd) l\u00e0 h\u1ee3p l\u1ec7, nh\u01b0ng c\u00e1c kh\u00f3a ngo\u1ea1i v\u00f2ng l\u1eb7p kh\u00f4ng ki\u1ec3m so\u00e1t \u0111\u01b0\u1ee3c c\u00f3 th\u1ec3 l\u00e0m h\u1ecfng c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/p>\n
T\u1ea1i sao \u0111i\u1ec1u n\u00e0y l\u00e0m h\u1ecfng h\u1ec7 th\u1ed1ng<\/h3>\n\n- L\u1ed7i kh\u1edfi t\u1ea1o:<\/strong> Trong qu\u00e1 tr\u00ecnh tri\u1ec3n khai, b\u1ed9 \u0111\u1ed9ng c\u01a1 c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u00f3 th\u1ec3 t\u1eeb ch\u1ed1i vi\u1ec7c t\u1ea1o r\u00e0ng bu\u1ed9c kh\u00f3a ngo\u1ea1i n\u1ebfu t\u1ed3n t\u1ea1i tham chi\u1ebfu v\u00f2ng l\u1eb7p (v\u00ed d\u1ee5: B\u1ea3ng A tham chi\u1ebfu B, v\u00e0 B tham chi\u1ebfu A) tr\u1eeb khi \u0111\u01b0\u1ee3c x\u1eed l\u00fd b\u1eb1ng c\u00e1c r\u00e0ng bu\u1ed9c ho\u00e3n l\u1ea1i.<\/li>\n
- Tr\u00e0n ng\u0103n x\u1ebfp truy v\u1ea5n:<\/strong>C\u00e1c truy v\u1ea5n \u0111\u1ec7 quy \u0111i qua nh\u1eefng v\u00f2ng l\u1eb7p n\u00e0y m\u00e0 kh\u00f4ng c\u00f3 \u0111i\u1ec1u ki\u1ec7n d\u1eebng c\u00f3 th\u1ec3 ti\u00eau th\u1ee5 to\u00e0n b\u1ed9 b\u1ed9 nh\u1edb s\u1eb5n c\u00f3.<\/li>\n
- Vi ph\u1ea1m t\u00ednh to\u00e0n v\u1eb9n tham chi\u1ebfu:<\/strong>X\u00f3a b\u1ea3ng cha c\u00f3 th\u1ec3 th\u1ea5t b\u1ea1i n\u1ebfu c\u00e1c b\u1ea3ng con ch\u01b0a \u0111\u01b0\u1ee3c d\u1ecdn d\u1eb9p, nh\u01b0ng vi\u1ec7c d\u1ecdn d\u1eb9p c\u00e1c b\u1ea3ng con c\u0169ng c\u00f3 th\u1ec3 th\u1ea5t b\u1ea1i do c\u00e1c ph\u1ee5 thu\u1ed9c kh\u00e1c.<\/li>\n<\/ul>\n
C\u00e1ch kh\u1eafc ph\u1ee5c<\/h3>\n\n- S\u1eed d\u1ee5ng R\u00e0ng bu\u1ed9c ho\u00e3n l\u1ea1i<\/strong> n\u1ebfu c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n h\u1ed7 tr\u1ee3 ch\u00fang, cho ph\u00e9p c\u01a1 s\u1edf d\u1eef li\u1ec7u ki\u1ec3m tra c\u00e1c m\u1ed1i quan h\u1ec7 sau khi t\u1ea5t c\u1ea3 d\u1eef li\u1ec7u \u0111\u00e3 \u0111\u01b0\u1ee3c t\u1ea3i.<\/li>\n
- \u0110\u1ed1i v\u1edbi c\u00e1c b\u1ea3ng tham chi\u1ebfu t\u1ef1 th\u00e2n (nh\u01b0 danh m\u1ee5c), \u0111\u1ea3m b\u1ea3o kh\u00f3a ngo\u1ea1i c\u00f3 th\u1ec3 \u0111\u1ec3 tr\u1ed1ng \u0111\u1ec3 cho ph\u00e9p c\u00e1c n\u00fat g\u1ed1c.<\/li>\n
- Thi\u1ebft k\u1ebf l\u01b0\u1ee3c \u0111\u1ed3 \u0111\u1ec3 cho ph\u00e9p m\u1ed9t c\u1ea5u tr\u00fac ph\u00e2n c\u1ea5p logic m\u00e0 kh\u00f4ng bu\u1ed9c ph\u1ea3i c\u00f3 v\u00f2ng l\u1eb7p kh\u00f3a ngo\u1ea1i v\u1eadt l\u00fd \u1edf m\u1ecdi c\u1ea5p \u0111\u1ed9.<\/li>\n
- Th\u1ef1c hi\u1ec7n x\u00f3a m\u1ec1m \u0111\u1ec3 qu\u1ea3n l\u00fd c\u00e1c thao t\u00e1c x\u00f3a lan truy\u1ec1n m\u1ed9t c\u00e1ch an to\u00e0n.<\/li>\n<\/ul>\n
5. Quy \u01b0\u1edbc \u0111\u1eb7t t\u00ean kh\u00f4ng nh\u1ea5t qu\u00e1n \ud83d\udcdd<\/h2>\n
T\u00ean l\u00e0 giao di\u1ec7n gi\u1eefa con ng\u01b0\u1eddi v\u00e0 m\u00e1y m\u00f3c. Vi\u1ec7c \u0111\u1eb7t t\u00ean kh\u00f4ng nh\u1ea5t qu\u00e1n trong t\u00ean b\u1ea3ng v\u00e0 c\u1ed9t khi\u1ebfn l\u01b0\u1ee3c \u0111\u1ed3 tr\u1edf n\u00ean kh\u00f3 hi\u1ec3u, kh\u00f3 b\u1ea3o tr\u00ec v\u00e0 truy v\u1ea5n. \u0110i\u1ec1u n\u00e0y th\u01b0\u1eddng xu\u1ea5t ph\u00e1t t\u1eeb vi\u1ec7c thi\u1ebfu m\u1ed9t h\u01b0\u1edbng d\u1eabn phong c\u00e1ch chung.<\/p>\n
C\u00e1c v\u1ea5n \u0111\u1ec1 c\u1ee5 th\u1ec3<\/h3>\n\n- Nhi\u1ec1u ch\u1eef hoa v\u00e0 th\u01b0\u1eddng:<\/strong>Pha tr\u1ed9n
camelCase<\/code>, snake_case<\/code>, v\u00e0 PascalCase<\/code> khi\u1ebfn c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n khi truy v\u1ea5n d\u1eef li\u1ec7u b\u1ecb nh\u1ea7m l\u1eabn.<\/li>\n- T\u1eeb kh\u00f3a \u0111\u01b0\u1ee3c b\u1ea3o l\u01b0u:<\/strong> S\u1eed d\u1ee5ng t\u00ean nh\u01b0
order<\/code>, group<\/code>, ho\u1eb7c user<\/code> m\u00e0 kh\u00f4ng tr\u1ed1n tr\u00e1nh c\u00f3 th\u1ec3 g\u00e2y l\u1ed7i c\u00fa ph\u00e1p trong c\u00e1c truy v\u1ea5n SQL.<\/li>\n- Vi\u1ebft t\u1eaft:<\/strong> S\u1eed d\u1ee5ng
usr_id<\/code> so v\u1edbi user_id<\/code> so v\u1edbi uid<\/code> trong c\u00e1c b\u1ea3ng kh\u00e1c nhau l\u00e0m gi\u1ea3m \u0111\u1ed9 r\u00f5 r\u00e0ng.<\/li>\n- \u0110\u1ed9 d\u00e0i vs Ng\u1eafn g\u1ecdn:<\/strong> M\u1ed9t s\u1ed1 c\u1ed9t qu\u00e1 d\u00e0i, trong khi nh\u1eefng c\u1ed9t kh\u00e1c l\u00e0 c\u00e1c vi\u1ebft t\u1eaft kh\u00f3 hi\u1ec3u.<\/li>\n<\/ul>\n
Thi\u1ebft l\u1eadp m\u1ed9t Ti\u00eau chu\u1ea9n<\/h3>\n\n- \u00c1p d\u1ee5ng chi\u1ebfn l\u01b0\u1ee3c vi\u1ebft hoa nh\u1ea5t qu\u00e1n (v\u00ed d\u1ee5 nh\u01b0
snake_case<\/code> cho c\u00e1c b\u1ea3ng SQL \u0111\u01b0\u1ee3c khuy\u1ebfn ngh\u1ecb r\u1ed9ng r\u00e3i).<\/li>\n- S\u1eed d\u1ee5ng t\u00ean m\u00f4 t\u1ea3 ph\u1ea3n \u00e1nh \u00fd ngh\u0129a kinh doanh, ch\u1ee9 kh\u00f4ng ph\u1ea3i chi ti\u1ebft tri\u1ec3n khai n\u1ed9i b\u1ed9.<\/li>\n
- Tr\u00e1nh ho\u00e0n to\u00e0n c\u00e1c t\u1eeb kh\u00f3a \u0111\u01b0\u1ee3c b\u1ea3o l\u01b0u. N\u1ebfu kh\u00f4ng th\u1ec3 tr\u00e1nh \u0111\u01b0\u1ee3c, h\u00e3y bao ch\u00fang trong d\u1ea5u ngo\u1eb7c k\u00e9p ho\u1eb7c d\u1ea5u ngo\u1eb7c \u0111\u01a1n ph\u00f9 h\u1ee3p v\u1edbi h\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/li>\n
- Ti\u00eau chu\u1ea9n h\u00f3a t\u00ean b\u1ea3ng s\u1ed1 \u00edt so v\u1edbi s\u1ed1 nhi\u1ec1u. Ch\u1ecdn m\u1ed9t c\u00e1ch v\u00e0 tu\u00e2n theo n\u00f3 (v\u00ed d\u1ee5 nh\u01b0
users<\/code> so v\u1edbi user<\/code>).<\/li>\n- Ti\u1ec1n t\u1ed1 c\u00e1c c\u1ed9t kh\u00f3a ngo\u1ea1i b\u1eb1ng t\u00ean b\u1ea3ng tham chi\u1ebfu (v\u00ed d\u1ee5 nh\u01b0
user_id<\/code>) \u0111\u1ec3 l\u00e0m r\u00f5 m\u1ed1i quan h\u1ec7.<\/li>\n<\/ul>\n6. G\u00e1n c\u1ee9ng gi\u00e1 tr\u1ecb trong l\u01b0\u1ee3c \u0111\u1ed3 \ud83d\uded1<\/h2>\n
C\u00e1c nh\u00e0 thi\u1ebft k\u1ebf \u0111\u00f4i khi nh\u00fang c\u00e1c gi\u00e1 tr\u1ecb kinh doanh c\u1ee5 th\u1ec3 tr\u1ef1c ti\u1ebfp v\u00e0o c\u1ea5u tr\u00fac c\u01a1 s\u1edf d\u1eef li\u1ec7u, ch\u1eb3ng h\u1ea1n nh\u01b0 s\u1eed d\u1ee5ng m\u1ed9t c\u1ed9t \u0111\u1ec3 l\u01b0u m\u00e3 tr\u1ea1ng th\u00e1i c\u1ee5 th\u1ec3 nh\u01b0 active<\/code> ho\u1eb7c inactive<\/code> thay v\u00ec s\u1eed d\u1ee5ng m\u1ed9t tr\u01b0\u1eddng tr\u1ea1ng th\u00e1i chung, ho\u1eb7c m\u00e3 h\u00f3a c\u1ee9ng c\u00e1c lo\u1ea1i ti\u1ec1n t\u1ec7.<\/p>\nT\u00e1c \u0111\u1ed9ng \u0111\u1ebfn t\u00ednh linh ho\u1ea1t<\/h3>\n\n- Thay \u0111\u1ed5i l\u01b0\u1ee3c \u0111\u1ed3:<\/strong> N\u1ebfu c\u1ea7n m\u1ed9t tr\u1ea1ng th\u00e1i m\u1edbi, b\u1ea1n c\u00f3 th\u1ec3 ph\u1ea3i thay \u0111\u1ed5i c\u1ea5u tr\u00fac b\u1ea3ng ho\u1eb7c th\u00eam c\u1ed9t m\u1edbi, d\u1eabn \u0111\u1ebfn th\u1eddi gian ng\u1eebng ho\u1ea1t \u0111\u1ed9ng khi tri\u1ec3n khai.<\/li>\n
- X\u00e1c th\u1ef1c d\u1eef li\u1ec7u:<\/strong> M\u00e3 \u1ee9ng d\u1ee5ng th\u01b0\u1eddng x\u00e1c th\u1ef1c c\u00e1c gi\u00e1 tr\u1ecb n\u00e0y, nh\u01b0ng l\u01b0\u1ee3c \u0111\u1ed3 c\u01a1 s\u1edf d\u1eef li\u1ec7u n\u00ean \u0111\u1ea3m b\u1ea3o c\u00e1c ph\u1ea1m vi ho\u1eb7c t\u1eadp h\u1ee3p h\u1ee3p l\u1ec7 th\u00f4ng qua r\u00e0ng bu\u1ed9c.<\/li>\n
- V\u1ea5n \u0111\u1ec1 \u0111\u1ecba ph\u01b0\u01a1ng h\u00f3a:<\/strong>M\u00e3 h\u00f3a c\u1ee9ng c\u00e1c gi\u00e1 tr\u1ecb v\u0103n b\u1ea3n nh\u01b0
USD<\/code> ho\u1eb7cTi\u1ebfng Anh<\/code> khi\u1ebfn vi\u1ec7c m\u1edf r\u1ed9ng to\u00e0n c\u1ea7u tr\u1edf n\u00ean kh\u00f3 kh\u0103n.<\/li>\n<\/ul>\nT\u00e1i c\u1ea5u tr\u00fac \u0111\u1ec3 m\u1edf r\u1ed9ng quy m\u00f4<\/h3>\n\n- S\u1eed d\u1ee5ngB\u1ea3ng tra c\u1ee9u<\/strong> cho b\u1ea5t k\u1ef3 t\u1eadp h\u1ee3p gi\u00e1 tr\u1ecb n\u00e0o c\u00f3 th\u1ec3 thay \u0111\u1ed5i ho\u1eb7c m\u1edf r\u1ed9ng (v\u00ed d\u1ee5: Tr\u1ea1ng th\u00e1i, Ti\u1ec1n t\u1ec7, Qu\u1ed1c gia).<\/li>\n
- Th\u1ef1c hi\u1ec7nR\u00e0ng bu\u1ed9c ki\u1ec3m tra<\/strong> \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o ch\u1ec9 c\u00f3 c\u00e1c gi\u00e1 tr\u1ecb h\u1ee3p l\u1ec7 \u0111\u01b0\u1ee3c nh\u1eadp, nh\u01b0ng gi\u1eef \u0111\u1ecbnh ngh\u0129a c\u1ee7a c\u00e1c gi\u00e1 tr\u1ecb \u0111\u00f3 trong \u1ee9ng d\u1ee5ng ho\u1eb7c trong m\u1ed9t b\u1ea3ng c\u1ea5u h\u00ecnh ri\u00eang bi\u1ec7t.<\/li>\n
- Ch\u1ec9 s\u1eed d\u1ee5ng ki\u1ec3u Enum n\u1ebfu h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u h\u1ed7 tr\u1ee3 ch\u00fang m\u1ed9t c\u00e1ch v\u1eefng ch\u1eafc v\u00e0 t\u1eadp h\u1ee3p gi\u00e1 tr\u1ecb th\u1ef1c s\u1ef1 c\u1ed1 \u0111\u1ecbnh.<\/li>\n
- T\u00e1ch d\u1eef li\u1ec7u c\u1ea5u h\u00ecnh kh\u1ecfi d\u1eef li\u1ec7u giao d\u1ecbch.<\/li>\n<\/ul>\n
7. B\u1ecf qua kh\u1ea3 n\u0103ng m\u1edf r\u1ed9ng trong t\u01b0\u01a1ng lai \ud83d\udcc8<\/h2>\n
Nhi\u1ec1u s\u01a1 \u0111\u1ed3 ERD \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf cho k\u00edch th\u01b0\u1edbc t\u1eadp d\u1eef li\u1ec7u hi\u1ec7n t\u1ea1i m\u00e0 kh\u00f4ng t\u00ednh \u0111\u1ebfn s\u1ef1 ph\u00e1t tri\u1ec3n. M\u1ed9t l\u01b0\u1ee3c \u0111\u1ed3 ho\u1ea1t \u0111\u1ed9ng t\u1ed1t v\u1edbi 1.000 b\u1ea3n ghi c\u00f3 th\u1ec3 th\u1ea5t b\u1ea1i nghi\u00eam tr\u1ecdng khi \u0111\u1ea1t \u0111\u1ebfn 10 tri\u1ec7u b\u1ea3n ghi do c\u00e1c v\u1ea5n \u0111\u1ec1 v\u1ec1 kh\u00f3a, ch\u1ec9 m\u1ee5c ho\u1eb7c chia t\u00e1ch d\u1eef li\u1ec7u.<\/p>\n
Nh\u1eefng sai l\u1ea7m v\u1ec1 kh\u1ea3 n\u0103ng m\u1edf r\u1ed9ng<\/h3>\n\n- C\u00e1c tr\u01b0\u1eddng v\u0103n b\u1ea3n l\u1edbn:<\/strong>L\u01b0u tr\u1eef c\u00e1c kh\u1ed1i d\u1eef li\u1ec7u l\u1edbn ho\u1eb7c chu\u1ed7i v\u0103n b\u1ea3n d\u00e0i trong b\u1ea3ng ch\u00ednh c\u00f3 th\u1ec3 l\u00e0m t\u0103ng k\u00edch th\u01b0\u1edbc ch\u1ec9 m\u1ee5c v\u00e0 l\u00e0m ch\u1eadm thao t\u00e1c \u0111\u1ecdc.<\/li>\n
- Thi\u1ebfu kh\u00f3a chia t\u00e1ch d\u1eef li\u1ec7u:<\/strong> N\u1ebfu l\u01b0\u1ee3c \u0111\u1ed3 kh\u00f4ng t\u00ednh \u0111\u1ebfn c\u00e1ch d\u1eef li\u1ec7u s\u1ebd \u0111\u01b0\u1ee3c chia nh\u1ecf ho\u1eb7c ph\u00e2n v\u00f9ng (v\u00ed d\u1ee5: theo ng\u00e0y ho\u1eb7c khu v\u1ef1c), vi\u1ec7c m\u1edf r\u1ed9ng ngang trong t\u01b0\u01a1ng lai s\u1ebd tr\u1edf th\u00e0nh m\u1ed9t thay \u0111\u1ed5i l\u1edbn.<\/li>\n
- Thi\u1ebfu ch\u1ec9 m\u1ee5c:<\/strong> Kh\u00f4ng l\u01b0\u1eddng tr\u01b0\u1edbc \u0111\u01b0\u1ee3c c\u00e1c c\u1ed9t n\u00e0o s\u1ebd \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 l\u1ecdc ho\u1eb7c s\u1eafp x\u1ebfp trong t\u01b0\u01a1ng lai d\u1eabn \u0111\u1ebfn c\u00e1c \u0111i\u1ec3m ngh\u1ebdn hi\u1ec7u su\u1ea5t.<\/li>\n
- M\u1eabu vi\u1ebft nhi\u1ec1u:<\/strong>M\u1ed9t thi\u1ebft k\u1ebf \u0111\u01b0\u1ee3c t\u1ed1i \u01b0u h\u00f3a cho thao t\u00e1c \u0111\u1ecdc c\u00f3 th\u1ec3 b\u1ecb ngh\u1ebdn khi th\u1ef1c hi\u1ec7n vi\u1ebft v\u1edbi kh\u1ed1i l\u01b0\u1ee3ng l\u1edbn do c\u01a1 ch\u1ebf kh\u00f3a tr\u00ean c\u00e1c kh\u00f3a ngo\u1ea1i.<\/li>\n<\/ul>\n
Thi\u1ebft k\u1ebf \u0111\u1ec3 ph\u00e1t tri\u1ec3n<\/h3>\n\n- Xem l\u1ea1i T\u1ef7 l\u1ec7 \u0111\u1ecdc\/vi\u1ebft<\/strong> c\u1ee7a \u1ee9ng d\u1ee5ng c\u1ee7a b\u1ea1n. N\u1ebfu n\u00f3 c\u00f3 xu h\u01b0\u1edbng vi\u1ebft nhi\u1ec1u, h\u00e3y t\u1ed1i thi\u1ec3u h\u00f3a c\u00e1c r\u00e0ng bu\u1ed9c kh\u00f3a ngo\u1ea1i g\u00e2y ra hi\u1ec7n t\u01b0\u1ee3ng kh\u00f3a.<\/li>\n
- Thi\u1ebft k\u1ebf Kh\u00f3a ph\u00e2n v\u00f9ng<\/strong> v\u00e0o s\u01a1 \u0111\u1ed3 ch\u00ednh c\u1ee7a b\u1ea1n. \u0110\u1ea3m b\u1ea3o m\u1ecdi b\u1ea3ng \u0111\u1ec1u c\u00f3 m\u1ed9t c\u1ed9t c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 chia d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch h\u1ee3p l\u00fd.<\/li>\n
- T\u00e1ch d\u1eef li\u1ec7u v\u0103n b\u1ea3n l\u1edbn v\u00e0o m\u1ed9t b\u1ea3ng ri\u00eang bi\u1ec7t (m\u1ed1i quan h\u1ec7 1:1) \u0111\u1ec3 gi\u1eef cho ch\u1ec9 m\u1ee5c ch\u00ednh lu\u00f4n g\u1ecdn nh\u1eb9.<\/li>\n
- L\u00ean k\u1ebf ho\u1ea1ch cho X\u00f3a m\u1ec1m<\/strong> thay v\u00ec x\u00f3a c\u1ee9ng \u0111\u1ec3 b\u1ea3o t\u1ed3n l\u1ecbch s\u1eed d\u1eef li\u1ec7u m\u00e0 kh\u00f4ng \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn hi\u1ec7u su\u1ea5t truy v\u1ea5n hi\u1ec7n t\u1ea1i.<\/li>\n<\/ul>\n
T\u00f3m t\u1eaft c\u00e1c th\u1ef1c h\u00e0nh t\u1ed1t nh\u1ea5t \ud83d\udccb<\/h2>\n
\u0110\u1ec3 \u0111\u1ea3m b\u1ea3o c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n lu\u00f4n \u1ed5n \u0111\u1ecbnh v\u00e0 d\u1ec5 b\u1ea3o tr\u00ec, h\u00e3y xem x\u00e9t s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 c\u1ee7a b\u1ea1n theo danh s\u00e1ch ki\u1ec3m tra sau tr\u01b0\u1edbc khi tri\u1ec3n khai.<\/p>\n
\n- Kh\u00f3a:<\/strong> M\u1ed7i b\u1ea3ng \u0111\u1ec1u c\u00f3 kh\u00f3a ch\u00ednh. C\u00e1c kh\u00f3a ngo\u1ea1i \u0111\u01b0\u1ee3c l\u1eadp ch\u1ec9 m\u1ee5c.<\/li>\n
- M\u1ed1i quan h\u1ec7:<\/strong> T\u00ednh cardinality \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh r\u00f5 r\u00e0ng. M\u1ed1i quan h\u1ec7 nhi\u1ec1u-nhi\u1ec1u s\u1eed d\u1ee5ng b\u1ea3ng li\u00ean k\u1ebft.<\/li>\n
- Chu\u1ea9n h\u00f3a:<\/strong> S\u1ef1 tr\u00f9ng l\u1eb7p d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c gi\u1ea3m thi\u1ec3u theo ti\u00eau chu\u1ea9n 3NF.<\/li>\n
- Ph\u1ee5 thu\u1ed9c:<\/strong> Kh\u00f4ng c\u00f3 v\u00f2ng l\u1eb7p kh\u00f3a ngo\u1ea1i v\u00f2ng m\u00e0 kh\u00f4ng c\u00f3 r\u00e0ng bu\u1ed9c ho\u00e3n l\u1ea1i.<\/li>\n
- \u0110\u1eb7t t\u00ean:<\/strong> S\u1eed d\u1ee5ng c\u00e1ch vi\u1ebft hoa nh\u1ea5t qu\u00e1n v\u00e0 t\u00ean m\u00f4 t\u1ea3 tr\u00ean to\u00e0n b\u1ed9 h\u1ec7 th\u1ed1ng.<\/li>\n
- Gi\u00e1 tr\u1ecb:<\/strong> Kh\u00f4ng c\u00f3 logic kinh doanh \u0111\u01b0\u1ee3c ghi c\u1ee9ng trong c\u1ea5u tr\u00fac l\u01b0\u1ee3c \u0111\u1ed3.<\/li>\n
- M\u1edf r\u1ed9ng:<\/strong> L\u01b0\u1ee3c \u0111\u1ed3 xem x\u00e9t c\u00e1c chi\u1ebfn l\u01b0\u1ee3c ph\u00e2n v\u00f9ng v\u00e0 l\u1eadp ch\u1ec9 m\u1ee5c \u0111\u1ec3 x\u1eed l\u00fd t\u1ea3i trong t\u01b0\u01a1ng lai.<\/li>\n<\/ul>\n
Suy ngh\u0129 cu\u1ed1i c\u00f9ng v\u1ec1 m\u00f4 h\u00ecnh h\u00f3a d\u1eef li\u1ec7u \ud83e\udde0<\/h2>\n
X\u00e2y d\u1ef1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u kh\u00f4ng ch\u1ec9 \u0111\u01a1n thu\u1ea7n l\u00e0 vi\u1ebftCREATE TABLE<\/code> c\u00e1c c\u00e2u l\u1ec7nh. \u0110\u00f3 l\u00e0 vi\u1ec7c m\u00f4 h\u00ecnh h\u00f3a th\u1ef1c t\u1ebf c\u1ee7a c\u00e1c quy tr\u00ecnh kinh doanh c\u1ee7a b\u1ea1n th\u00e0nh m\u1ed9t c\u1ea5u tr\u00fac logic m\u00e0 m\u00e1y t\u00ednh c\u00f3 th\u1ec3 x\u1eed l\u00fd m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3. Chi ph\u00ed s\u1eeda l\u1ed7i l\u01b0\u1ee3c \u0111\u1ed3 t\u0103ng theo c\u1ea5p s\u1ed1 nh\u00e2n n\u1ebfu ph\u00e1t hi\u1ec7n l\u1ed7i c\u00e0ng mu\u1ed9n trong chu k\u1ef3 ph\u00e1t tri\u1ec3n.<\/p>\nB\u1eb1ng c\u00e1ch tr\u00e1nh b\u1ea3y sai l\u1ea7m ph\u1ed5 bi\u1ebfn n\u00e0y, b\u1ea1n s\u1ebd gi\u1ea3m n\u1ee3 k\u1ef9 thu\u1eadt v\u00e0 t\u1ea1o n\u1ec1n t\u1ea3ng h\u1ed7 tr\u1ee3 c\u00e1c truy v\u1ea5n ph\u1ee9c t\u1ea1p v\u00e0 giao d\u1ecbch kh\u1ed1i l\u01b0\u1ee3ng l\u1edbn. H\u00e3y \u01b0u ti\u00ean s\u1ef1 r\u00f5 r\u00e0ng, t\u00ednh to\u00e0n v\u1eb9n v\u00e0 t\u00ednh linh ho\u1ea1t trong s\u01a1 \u0111\u1ed3 c\u1ee7a b\u1ea1n. M\u1ed9t s\u01a1 \u0111\u1ed3 ERD \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf t\u1ed1t s\u1ebd v\u00f4 h\u00ecnh v\u1edbi ng\u01b0\u1eddi d\u00f9ng cu\u1ed1i nh\u01b0ng l\u1ea1i thi\u1ebft y\u1ebfu cho s\u1ef1 b\u1ec1n v\u1eefng c\u1ee7a h\u1ec7 th\u1ed1ng.<\/p>\n
D\u00e0nh th\u1eddi gian xem x\u00e9t l\u1ea1i l\u01b0\u1ee3c \u0111\u1ed3 c\u1ee7a b\u1ea1n v\u1edbi c\u00e1i nh\u00ecn m\u1edbi m\u1ebb ho\u1eb7c th\u00f4ng qua quy tr\u00ecnh ki\u1ec3m tra b\u1edfi \u0111\u1ed3ng nghi\u1ec7p. \u0110\u1eb7t c\u00e2u h\u1ecfi v\u1ec1 l\u00fd do t\u1ea1i sao m\u1ed9t m\u1ed1i quan h\u1ec7 t\u1ed3n t\u1ea1i v\u00e0 n\u00f3 s\u1ebd ho\u1ea1t \u0111\u1ed9ng th\u1ebf n\u00e0o khi ch\u1ecbu t\u1ea3i. S\u1ef1 c\u1ea9n tr\u1ecdng n\u00e0y s\u1ebd mang l\u1ea1i l\u1ee3i \u00edch cho \u0111\u1ed9 tin c\u1eady c\u1ee7a h\u1ec7 th\u1ed1ng v\u00e0 n\u0103ng su\u1ea5t ph\u00e1t tri\u1ec3n c\u1ee7a nh\u00e0 ph\u00e1t tri\u1ec3n trong t\u01b0\u01a1ng lai.<\/p>\n","protected":false},"excerpt":{"rendered":"
Thi\u1ebft k\u1ebf m\u1ed9t c\u1ea5u tr\u00fac d\u1eef li\u1ec7u v\u1eefng ch\u1eafc l\u00e0 n\u1ec1n t\u1ea3ng c\u1ee7a b\u1ea5t k\u1ef3 h\u1ec7 th\u1ed1ng ph\u1ea7n m\u1ec1m \u0111\u00e1ng tin c\u1eady n\u00e0o. S\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 (ERD)…<\/p>\n","protected":false},"author":1,"featured_media":1604,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_yoast_wpseo_title":"7 Sai l\u1ea7m trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 khi\u1ebfn c\u01a1 s\u1edf d\u1eef li\u1ec7u b\u1ecb h\u1ecfng (v\u00e0 c\u00e1ch tr\u00e1nh ch\u00fang) \ud83d\udee0\ufe0f","_yoast_wpseo_metadesc":"Kh\u00e1m ph\u00e1 nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 l\u00e0m \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u. H\u1ecdc c\u00e1ch thi\u1ebft k\u1ebf c\u00e1c l\u01b0\u1ee3c \u0111\u1ed3 v\u1eefng ch\u1eafc v\u00e0 tr\u00e1nh vi\u1ec7c t\u00e1i c\u1ea5u tr\u00fac t\u1ed1n k\u00e9m.","fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[88],"tags":[84,87],"class_list":["post-1603","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-erd","tag-academic","tag-erd"],"yoast_head":"\n
7 Sai l\u1ea7m trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 khi\u1ebfn c\u01a1 s\u1edf d\u1eef li\u1ec7u b\u1ecb h\u1ecfng (v\u00e0 c\u00e1ch tr\u00e1nh ch\u00fang) \ud83d\udee0\ufe0f<\/title>\n<meta name=\"description\" content=\"Kh\u00e1m ph\u00e1 nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 l\u00e0m \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u. H\u1ecdc c\u00e1ch thi\u1ebft k\u1ebf c\u00e1c l\u01b0\u1ee3c \u0111\u1ed3 v\u1eefng ch\u1eafc v\u00e0 tr\u00e1nh vi\u1ec7c t\u00e1i c\u1ea5u tr\u00fac t\u1ed1n k\u00e9m.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.viz-read.com\/vi\/7-erd-mistakes-break-databases-avoid\/\" \/>\n<meta property=\"og:locale\" content=\"vi_VN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"7 Sai l\u1ea7m trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 khi\u1ebfn c\u01a1 s\u1edf d\u1eef li\u1ec7u b\u1ecb h\u1ecfng (v\u00e0 c\u00e1ch tr\u00e1nh ch\u00fang) \ud83d\udee0\ufe0f\" \/>\n<meta property=\"og:description\" content=\"Kh\u00e1m ph\u00e1 nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 l\u00e0m \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u. H\u1ecdc c\u00e1ch thi\u1ebft k\u1ebf c\u00e1c l\u01b0\u1ee3c \u0111\u1ed3 v\u1eefng ch\u1eafc v\u00e0 tr\u00e1nh vi\u1ec7c t\u00e1i c\u1ea5u tr\u00fac t\u1ed1n k\u00e9m.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.viz-read.com\/vi\/7-erd-mistakes-break-databases-avoid\/\" \/>\n<meta property=\"og:site_name\" content=\"Viz Read Vietnamese - AI, Software & Digital Insights\" \/>\n<meta property=\"article:published_time\" content=\"2026-03-24T23:50:44+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.viz-read.com\/vi\/wp-content\/uploads\/sites\/10\/2026\/03\/7-erd-mistakes-database-design-whimsical-infographic.jpg\" \/>\n\t<meta property=\"og:image:width\" content=\"1664\" \/>\n\t<meta property=\"og:image:height\" content=\"928\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/jpeg\" \/>\n<meta name=\"author\" content=\"vpadmin\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"\u0110\u01b0\u1ee3c vi\u1ebft b\u1edfi\" \/>\n\t<meta name=\"twitter:data1\" content=\"\" \/>\n\t<meta name=\"twitter:label2\" content=\"\u01af\u1edbc t\u00ednh th\u1eddi gian \u0111\u1ecdc\" \/>\n\t<meta name=\"twitter:data2\" content=\"22 ph\u00fat\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/www.viz-read.com\/vi\/7-erd-mistakes-break-databases-avoid\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/www.viz-read.com\/vi\/7-erd-mistakes-break-databases-avoid\/\"},\"author\":{\"name\":\"vpadmin\",\"@id\":\"https:\/\/www.viz-read.com\/vi\/#\/schema\/person\/26e014daa5bbdc9b97114eee89cc3936\"},\"headline\":\"7 L\u1ed7i ERD L\u00e0m H\u1ecfng C\u01a1 S\u1edf D\u1eef Li\u1ec7u (V\u00e0 C\u00e1ch Tr\u00e1nh Ch\u00fang)\",\"datePublished\":\"2026-03-24T23:50:44+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/www.viz-read.com\/vi\/7-erd-mistakes-break-databases-avoid\/\"},\"wordCount\":4303,\"publisher\":{\"@id\":\"https:\/\/www.viz-read.com\/vi\/#organization\"},\"image\":{\"@id\":\"https:\/\/www.viz-read.com\/vi\/7-erd-mistakes-break-databases-avoid\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/www.viz-read.com\/vi\/wp-content\/uploads\/sites\/10\/2026\/03\/7-erd-mistakes-database-design-whimsical-infographic.jpg\",\"keywords\":[\"academic\",\"erd\"],\"articleSection\":[\"ERD\"],\"inLanguage\":\"vi\"},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.viz-read.com\/vi\/7-erd-mistakes-break-databases-avoid\/\",\"url\":\"https:\/\/www.viz-read.com\/vi\/7-erd-mistakes-break-databases-avoid\/\",\"name\":\"7 Sai l\u1ea7m trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 khi\u1ebfn c\u01a1 s\u1edf d\u1eef li\u1ec7u b\u1ecb h\u1ecfng (v\u00e0 c\u00e1ch tr\u00e1nh ch\u00fang) \ud83d\udee0\ufe0f\",\"isPartOf\":{\"@id\":\"https:\/\/www.viz-read.com\/vi\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\/\/www.viz-read.com\/vi\/7-erd-mistakes-break-databases-avoid\/#primaryimage\"},\"image\":{\"@id\":\"https:\/\/www.viz-read.com\/vi\/7-erd-mistakes-break-databases-avoid\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/www.viz-read.com\/vi\/wp-content\/uploads\/sites\/10\/2026\/03\/7-erd-mistakes-database-design-whimsical-infographic.jpg\",\"datePublished\":\"2026-03-24T23:50:44+00:00\",\"description\":\"Kh\u00e1m ph\u00e1 nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 l\u00e0m \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u. 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C\u00e1ch Ti\u1ebfp C\u1eadn \u0110\u00fang<\/h3>\n\n- M\u00f4 h\u00ecnh h\u00f3a r\u00f5 r\u00e0ng c\u00e1c m\u1ed1i quan h\u1ec7 nhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng b\u1ea3ng giao nhau (b\u1ea3ng li\u00ean k\u1ebft) ch\u1ee9a c\u00e1c kh\u00f3a ngo\u1ea1i t\u1eeb c\u1ea3 hai b\u1ea3ng li\u00ean quan.<\/li>\n
- Ghi r\u00f5 cardinality tr\u00ean c\u00e1c \u0111\u01b0\u1eddng n\u1ed1i trong s\u01a1 \u0111\u1ed3.<\/li>\n
- \u00c1p d\u1ee5ng c\u00e1c r\u00e0ng bu\u1ed9c c\u01a1 s\u1edf d\u1eef li\u1ec7u (nh\u01b0 r\u00e0ng bu\u1ed9c UNIQUE tr\u00ean kh\u00f3a ngo\u1ea1i) \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o logic trong s\u01a1 \u0111\u1ed3 \u0111\u01b0\u1ee3c th\u1ef1c thi.<\/li>\n<\/ul>\n
\n\n\nLo\u1ea1i quan h\u1ec7<\/th>\n Chi\u1ebfn l\u01b0\u1ee3c tri\u1ec3n khai<\/th>\n L\u1ed7i ph\u1ed5 bi\u1ebfn<\/th>\n<\/tr>\n<\/thead>\n \n\nM\u1ed9t-\u0111\u1ed1i-m\u1ed9t<\/td>\n Kh\u00f3a ngo\u1ea1i trong m\u1ed9t b\u1ea3ng v\u1edbi r\u00e0ng bu\u1ed9c UNIQUE<\/td>\n Th\u00eam kh\u00f3a ngo\u1ea1i v\u00e0o c\u1ea3 hai b\u1ea3ng m\u1ed9t c\u00e1ch kh\u00f4ng c\u1ea7n thi\u1ebft<\/td>\n<\/tr>\n \nM\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u<\/td>\n Kh\u00f3a ngo\u1ea1i trong b\u1ea3ng \u201cNhi\u1ec1u\u201d<\/td>\n L\u01b0u tr\u1eef d\u1eef li\u1ec7u cha trong b\u1ea3ng con (phi chu\u1ea9n h\u00f3a)<\/td>\n<\/tr>\n \nNhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u<\/td>\n B\u1ea3ng li\u00ean k\u1ebft trung gian<\/td>\n L\u01b0u tr\u1eef nhi\u1ec1u ID trong m\u1ed9t c\u1ed9t ph\u00e2n c\u00e1ch b\u1eb1ng d\u1ea5u ph\u1ea9y<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n3. B\u1ecf qua c\u00e1c ti\u00eau chu\u1ea9n chu\u1ea9n h\u00f3a \ud83d\udcc9<\/h2>\n
Chu\u1ea9n h\u00f3a l\u00e0 qu\u00e1 tr\u00ecnh t\u1ed5 ch\u1ee9c d\u1eef li\u1ec7u nh\u1eb1m gi\u1ea3m thi\u1ec3u s\u1ef1 tr\u00f9ng l\u1eb7p v\u00e0 c\u1ea3i thi\u1ec7n t\u00ednh to\u00e0n v\u1eb9n. Trong khi m\u1ed9t s\u1ed1 h\u1ec7 th\u1ed1ng hi\u1ec7n \u0111\u1ea1i ch\u1ea5p nh\u1eadn phi chu\u1ea9n h\u00f3a \u0111\u1ec3 t\u0103ng hi\u1ec7u su\u1ea5t \u0111\u1ecdc, nh\u01b0ng b\u1ecf qua ho\u00e0n to\u00e0n chu\u1ea9n h\u00f3a trong giai \u0111o\u1ea1n thi\u1ebft k\u1ebf s\u1ebd t\u1ea1o ra g\u00e1nh n\u1eb7ng b\u1ea3o tr\u00ec \u0111\u00e1ng k\u1ec3.<\/p>\n
R\u1ee7i ro c\u1ee7a vi\u1ec7c chu\u1ea9n h\u00f3a k\u00e9m<\/h3>\n\n- L\u1ed7i c\u1eadp nh\u1eadt:<\/strong> N\u1ebfu \u0111\u1ecba ch\u1ec9 kh\u00e1ch h\u00e0ng \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef trong n\u0103m b\u1ea3ng \u0111\u01a1n h\u00e0ng kh\u00e1c nhau, vi\u1ec7c c\u1eadp nh\u1eadt \u0111\u1ecba ch\u1ec9 c\u1ee7a h\u1ecd \u0111\u00f2i h\u1ecfi n\u0103m thao t\u00e1c c\u1eadp nh\u1eadt ri\u00eang bi\u1ec7t. N\u1ebfu m\u1ed9t thao t\u00e1c th\u1ea5t b\u1ea1i, d\u1eef li\u1ec7u s\u1ebd tr\u1edf n\u00ean kh\u00f4ng nh\u1ea5t qu\u00e1n.<\/li>\n
- L\u1ed7i ch\u00e8n:<\/strong> B\u1ea1n c\u00f3 th\u1ec3 kh\u00f4ng th\u1ec3 th\u00eam m\u1ed9t danh m\u1ee5c s\u1ea3n ph\u1ea9m m\u1edbi m\u00e0 kh\u00f4ng c\u1ea7n th\u00eam b\u1ea3n ghi s\u1ea3n ph\u1ea9m, bu\u1ed9c ph\u1ea3i t\u1ea1o d\u1eef li\u1ec7u gi\u1ea3.<\/li>\n
- L\u1ed7i x\u00f3a:<\/strong> Vi\u1ec7c x\u00f3a m\u1ed9t b\u1ea3n ghi c\u00f3 th\u1ec3 v\u00f4 t\u00ecnh lo\u1ea1i b\u1ecf d\u1eef li\u1ec7u quan tr\u1ecdng li\u00ean quan \u0111\u1ebfn c\u00e1c th\u1ef1c th\u1ec3 kh\u00e1c.<\/li>\n<\/ul>\n
H\u01b0\u1edbng d\u1eabn tri\u1ec3n khai<\/h3>\n\n- M\u1ee5c ti\u00eau h\u01b0\u1edbng t\u1edbi d\u1ea1ng chu\u1ea9n h\u00f3a th\u1ee9 ba (3NF) nh\u01b0 m\u1ed9t n\u1ec1n t\u1ea3ng. \u0110i\u1ec1u n\u00e0y \u0111\u1ea3m b\u1ea3o r\u1eb1ng c\u00e1c c\u1ed9t ch\u1ec9 ph\u1ee5 thu\u1ed9c v\u00e0o kh\u00f3a ch\u00ednh.<\/li>\n
- X\u00e1c \u0111\u1ecbnh c\u00e1c ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u n\u01a1i m\u1ed9t c\u1ed9t kh\u00f4ng ph\u1ea3i kh\u00f3a ph\u1ee5 thu\u1ed9c v\u00e0o m\u1ed9t c\u1ed9t kh\u00f4ng ph\u1ea3i kh\u00f3a kh\u00e1c.<\/li>\n
- T\u00e1ch bi\u1ec7t c\u00e1c th\u1ef1c th\u1ec3 ri\u00eang bi\u1ec7t. N\u1ebfu m\u1ed9t b\u1ea3ng ch\u1ee9a th\u00f4ng tin v\u1ec1 c\u1ea3 \u201c\u0110\u01a1n h\u00e0ng\u201d v\u00e0 \u201cKh\u00e1ch h\u00e0ng\u201d, h\u00e3y t\u00e1ch ch\u00fang ra.<\/li>\n
- Ch\u1ec9 phi chu\u1ea9n h\u00f3a sau khi ph\u00e2n t\u00edch hi\u1ec7u su\u1ea5t truy v\u1ea5n. \u0110\u1eebng t\u1ed1i \u01b0u h\u00f3a tr\u01b0\u1edbc cho t\u1ed1c \u0111\u1ed9 m\u00e0 \u0111\u00e1nh \u0111\u1ed5i t\u00ednh to\u00e0n v\u1eb9n.<\/li>\n<\/ul>\n
4. T\u1ea1o ra c\u00e1c ph\u1ee5 thu\u1ed9c v\u00f2ng l\u1eb7p \ud83d\udd01<\/h2>\n
C\u00e1c ph\u1ee5 thu\u1ed9c v\u00f2ng x\u1ea3y ra khi c\u00e1c b\u1ea3ng tham chi\u1ebfu l\u1eabn nhau theo m\u1ed9t v\u00f2ng l\u1eb7p, ng\u0103n c\u1ea3n qu\u00e1 tr\u00ecnh kh\u1edfi t\u1ea1o ho\u1eb7c g\u00e2y ra \u0111\u1ec7 quy v\u00f4 h\u1ea1n trong truy v\u1ea5n. M\u1eb7c d\u00f9 c\u00e1c m\u1ed1i quan h\u1ec7 \u0111\u1ec7 quy (nh\u01b0 s\u01a1 \u0111\u1ed3 t\u1ed5 ch\u1ee9c n\u01a1i m\u1ed9t nh\u00e2n vi\u00ean c\u00f3 ng\u01b0\u1eddi qu\u1ea3n l\u00fd) l\u00e0 h\u1ee3p l\u1ec7, nh\u01b0ng c\u00e1c kh\u00f3a ngo\u1ea1i v\u00f2ng l\u1eb7p kh\u00f4ng ki\u1ec3m so\u00e1t \u0111\u01b0\u1ee3c c\u00f3 th\u1ec3 l\u00e0m h\u1ecfng c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/p>\n
T\u1ea1i sao \u0111i\u1ec1u n\u00e0y l\u00e0m h\u1ecfng h\u1ec7 th\u1ed1ng<\/h3>\n\n- L\u1ed7i kh\u1edfi t\u1ea1o:<\/strong> Trong qu\u00e1 tr\u00ecnh tri\u1ec3n khai, b\u1ed9 \u0111\u1ed9ng c\u01a1 c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u00f3 th\u1ec3 t\u1eeb ch\u1ed1i vi\u1ec7c t\u1ea1o r\u00e0ng bu\u1ed9c kh\u00f3a ngo\u1ea1i n\u1ebfu t\u1ed3n t\u1ea1i tham chi\u1ebfu v\u00f2ng l\u1eb7p (v\u00ed d\u1ee5: B\u1ea3ng A tham chi\u1ebfu B, v\u00e0 B tham chi\u1ebfu A) tr\u1eeb khi \u0111\u01b0\u1ee3c x\u1eed l\u00fd b\u1eb1ng c\u00e1c r\u00e0ng bu\u1ed9c ho\u00e3n l\u1ea1i.<\/li>\n
- Tr\u00e0n ng\u0103n x\u1ebfp truy v\u1ea5n:<\/strong>C\u00e1c truy v\u1ea5n \u0111\u1ec7 quy \u0111i qua nh\u1eefng v\u00f2ng l\u1eb7p n\u00e0y m\u00e0 kh\u00f4ng c\u00f3 \u0111i\u1ec1u ki\u1ec7n d\u1eebng c\u00f3 th\u1ec3 ti\u00eau th\u1ee5 to\u00e0n b\u1ed9 b\u1ed9 nh\u1edb s\u1eb5n c\u00f3.<\/li>\n
- Vi ph\u1ea1m t\u00ednh to\u00e0n v\u1eb9n tham chi\u1ebfu:<\/strong>X\u00f3a b\u1ea3ng cha c\u00f3 th\u1ec3 th\u1ea5t b\u1ea1i n\u1ebfu c\u00e1c b\u1ea3ng con ch\u01b0a \u0111\u01b0\u1ee3c d\u1ecdn d\u1eb9p, nh\u01b0ng vi\u1ec7c d\u1ecdn d\u1eb9p c\u00e1c b\u1ea3ng con c\u0169ng c\u00f3 th\u1ec3 th\u1ea5t b\u1ea1i do c\u00e1c ph\u1ee5 thu\u1ed9c kh\u00e1c.<\/li>\n<\/ul>\n
C\u00e1ch kh\u1eafc ph\u1ee5c<\/h3>\n\n- S\u1eed d\u1ee5ng R\u00e0ng bu\u1ed9c ho\u00e3n l\u1ea1i<\/strong> n\u1ebfu c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n h\u1ed7 tr\u1ee3 ch\u00fang, cho ph\u00e9p c\u01a1 s\u1edf d\u1eef li\u1ec7u ki\u1ec3m tra c\u00e1c m\u1ed1i quan h\u1ec7 sau khi t\u1ea5t c\u1ea3 d\u1eef li\u1ec7u \u0111\u00e3 \u0111\u01b0\u1ee3c t\u1ea3i.<\/li>\n
- \u0110\u1ed1i v\u1edbi c\u00e1c b\u1ea3ng tham chi\u1ebfu t\u1ef1 th\u00e2n (nh\u01b0 danh m\u1ee5c), \u0111\u1ea3m b\u1ea3o kh\u00f3a ngo\u1ea1i c\u00f3 th\u1ec3 \u0111\u1ec3 tr\u1ed1ng \u0111\u1ec3 cho ph\u00e9p c\u00e1c n\u00fat g\u1ed1c.<\/li>\n
- Thi\u1ebft k\u1ebf l\u01b0\u1ee3c \u0111\u1ed3 \u0111\u1ec3 cho ph\u00e9p m\u1ed9t c\u1ea5u tr\u00fac ph\u00e2n c\u1ea5p logic m\u00e0 kh\u00f4ng bu\u1ed9c ph\u1ea3i c\u00f3 v\u00f2ng l\u1eb7p kh\u00f3a ngo\u1ea1i v\u1eadt l\u00fd \u1edf m\u1ecdi c\u1ea5p \u0111\u1ed9.<\/li>\n
- Th\u1ef1c hi\u1ec7n x\u00f3a m\u1ec1m \u0111\u1ec3 qu\u1ea3n l\u00fd c\u00e1c thao t\u00e1c x\u00f3a lan truy\u1ec1n m\u1ed9t c\u00e1ch an to\u00e0n.<\/li>\n<\/ul>\n
5. Quy \u01b0\u1edbc \u0111\u1eb7t t\u00ean kh\u00f4ng nh\u1ea5t qu\u00e1n \ud83d\udcdd<\/h2>\n
T\u00ean l\u00e0 giao di\u1ec7n gi\u1eefa con ng\u01b0\u1eddi v\u00e0 m\u00e1y m\u00f3c. Vi\u1ec7c \u0111\u1eb7t t\u00ean kh\u00f4ng nh\u1ea5t qu\u00e1n trong t\u00ean b\u1ea3ng v\u00e0 c\u1ed9t khi\u1ebfn l\u01b0\u1ee3c \u0111\u1ed3 tr\u1edf n\u00ean kh\u00f3 hi\u1ec3u, kh\u00f3 b\u1ea3o tr\u00ec v\u00e0 truy v\u1ea5n. \u0110i\u1ec1u n\u00e0y th\u01b0\u1eddng xu\u1ea5t ph\u00e1t t\u1eeb vi\u1ec7c thi\u1ebfu m\u1ed9t h\u01b0\u1edbng d\u1eabn phong c\u00e1ch chung.<\/p>\n
C\u00e1c v\u1ea5n \u0111\u1ec1 c\u1ee5 th\u1ec3<\/h3>\n\n- Nhi\u1ec1u ch\u1eef hoa v\u00e0 th\u01b0\u1eddng:<\/strong>Pha tr\u1ed9n
camelCase<\/code>, snake_case<\/code>, v\u00e0 PascalCase<\/code> khi\u1ebfn c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n khi truy v\u1ea5n d\u1eef li\u1ec7u b\u1ecb nh\u1ea7m l\u1eabn.<\/li>\n- T\u1eeb kh\u00f3a \u0111\u01b0\u1ee3c b\u1ea3o l\u01b0u:<\/strong> S\u1eed d\u1ee5ng t\u00ean nh\u01b0
order<\/code>, group<\/code>, ho\u1eb7c user<\/code> m\u00e0 kh\u00f4ng tr\u1ed1n tr\u00e1nh c\u00f3 th\u1ec3 g\u00e2y l\u1ed7i c\u00fa ph\u00e1p trong c\u00e1c truy v\u1ea5n SQL.<\/li>\n- Vi\u1ebft t\u1eaft:<\/strong> S\u1eed d\u1ee5ng
usr_id<\/code> so v\u1edbi user_id<\/code> so v\u1edbi uid<\/code> trong c\u00e1c b\u1ea3ng kh\u00e1c nhau l\u00e0m gi\u1ea3m \u0111\u1ed9 r\u00f5 r\u00e0ng.<\/li>\n- \u0110\u1ed9 d\u00e0i vs Ng\u1eafn g\u1ecdn:<\/strong> M\u1ed9t s\u1ed1 c\u1ed9t qu\u00e1 d\u00e0i, trong khi nh\u1eefng c\u1ed9t kh\u00e1c l\u00e0 c\u00e1c vi\u1ebft t\u1eaft kh\u00f3 hi\u1ec3u.<\/li>\n<\/ul>\n
Thi\u1ebft l\u1eadp m\u1ed9t Ti\u00eau chu\u1ea9n<\/h3>\n\n- \u00c1p d\u1ee5ng chi\u1ebfn l\u01b0\u1ee3c vi\u1ebft hoa nh\u1ea5t qu\u00e1n (v\u00ed d\u1ee5 nh\u01b0
snake_case<\/code> cho c\u00e1c b\u1ea3ng SQL \u0111\u01b0\u1ee3c khuy\u1ebfn ngh\u1ecb r\u1ed9ng r\u00e3i).<\/li>\n- S\u1eed d\u1ee5ng t\u00ean m\u00f4 t\u1ea3 ph\u1ea3n \u00e1nh \u00fd ngh\u0129a kinh doanh, ch\u1ee9 kh\u00f4ng ph\u1ea3i chi ti\u1ebft tri\u1ec3n khai n\u1ed9i b\u1ed9.<\/li>\n
- Tr\u00e1nh ho\u00e0n to\u00e0n c\u00e1c t\u1eeb kh\u00f3a \u0111\u01b0\u1ee3c b\u1ea3o l\u01b0u. N\u1ebfu kh\u00f4ng th\u1ec3 tr\u00e1nh \u0111\u01b0\u1ee3c, h\u00e3y bao ch\u00fang trong d\u1ea5u ngo\u1eb7c k\u00e9p ho\u1eb7c d\u1ea5u ngo\u1eb7c \u0111\u01a1n ph\u00f9 h\u1ee3p v\u1edbi h\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/li>\n
- Ti\u00eau chu\u1ea9n h\u00f3a t\u00ean b\u1ea3ng s\u1ed1 \u00edt so v\u1edbi s\u1ed1 nhi\u1ec1u. Ch\u1ecdn m\u1ed9t c\u00e1ch v\u00e0 tu\u00e2n theo n\u00f3 (v\u00ed d\u1ee5 nh\u01b0
users<\/code> so v\u1edbi user<\/code>).<\/li>\n- Ti\u1ec1n t\u1ed1 c\u00e1c c\u1ed9t kh\u00f3a ngo\u1ea1i b\u1eb1ng t\u00ean b\u1ea3ng tham chi\u1ebfu (v\u00ed d\u1ee5 nh\u01b0
user_id<\/code>) \u0111\u1ec3 l\u00e0m r\u00f5 m\u1ed1i quan h\u1ec7.<\/li>\n<\/ul>\n6. G\u00e1n c\u1ee9ng gi\u00e1 tr\u1ecb trong l\u01b0\u1ee3c \u0111\u1ed3 \ud83d\uded1<\/h2>\n
C\u00e1c nh\u00e0 thi\u1ebft k\u1ebf \u0111\u00f4i khi nh\u00fang c\u00e1c gi\u00e1 tr\u1ecb kinh doanh c\u1ee5 th\u1ec3 tr\u1ef1c ti\u1ebfp v\u00e0o c\u1ea5u tr\u00fac c\u01a1 s\u1edf d\u1eef li\u1ec7u, ch\u1eb3ng h\u1ea1n nh\u01b0 s\u1eed d\u1ee5ng m\u1ed9t c\u1ed9t \u0111\u1ec3 l\u01b0u m\u00e3 tr\u1ea1ng th\u00e1i c\u1ee5 th\u1ec3 nh\u01b0 active<\/code> ho\u1eb7c inactive<\/code> thay v\u00ec s\u1eed d\u1ee5ng m\u1ed9t tr\u01b0\u1eddng tr\u1ea1ng th\u00e1i chung, ho\u1eb7c m\u00e3 h\u00f3a c\u1ee9ng c\u00e1c lo\u1ea1i ti\u1ec1n t\u1ec7.<\/p>\nT\u00e1c \u0111\u1ed9ng \u0111\u1ebfn t\u00ednh linh ho\u1ea1t<\/h3>\n\n- Thay \u0111\u1ed5i l\u01b0\u1ee3c \u0111\u1ed3:<\/strong> N\u1ebfu c\u1ea7n m\u1ed9t tr\u1ea1ng th\u00e1i m\u1edbi, b\u1ea1n c\u00f3 th\u1ec3 ph\u1ea3i thay \u0111\u1ed5i c\u1ea5u tr\u00fac b\u1ea3ng ho\u1eb7c th\u00eam c\u1ed9t m\u1edbi, d\u1eabn \u0111\u1ebfn th\u1eddi gian ng\u1eebng ho\u1ea1t \u0111\u1ed9ng khi tri\u1ec3n khai.<\/li>\n
- X\u00e1c th\u1ef1c d\u1eef li\u1ec7u:<\/strong> M\u00e3 \u1ee9ng d\u1ee5ng th\u01b0\u1eddng x\u00e1c th\u1ef1c c\u00e1c gi\u00e1 tr\u1ecb n\u00e0y, nh\u01b0ng l\u01b0\u1ee3c \u0111\u1ed3 c\u01a1 s\u1edf d\u1eef li\u1ec7u n\u00ean \u0111\u1ea3m b\u1ea3o c\u00e1c ph\u1ea1m vi ho\u1eb7c t\u1eadp h\u1ee3p h\u1ee3p l\u1ec7 th\u00f4ng qua r\u00e0ng bu\u1ed9c.<\/li>\n
- V\u1ea5n \u0111\u1ec1 \u0111\u1ecba ph\u01b0\u01a1ng h\u00f3a:<\/strong>M\u00e3 h\u00f3a c\u1ee9ng c\u00e1c gi\u00e1 tr\u1ecb v\u0103n b\u1ea3n nh\u01b0
USD<\/code> ho\u1eb7cTi\u1ebfng Anh<\/code> khi\u1ebfn vi\u1ec7c m\u1edf r\u1ed9ng to\u00e0n c\u1ea7u tr\u1edf n\u00ean kh\u00f3 kh\u0103n.<\/li>\n<\/ul>\nT\u00e1i c\u1ea5u tr\u00fac \u0111\u1ec3 m\u1edf r\u1ed9ng quy m\u00f4<\/h3>\n\n- S\u1eed d\u1ee5ngB\u1ea3ng tra c\u1ee9u<\/strong> cho b\u1ea5t k\u1ef3 t\u1eadp h\u1ee3p gi\u00e1 tr\u1ecb n\u00e0o c\u00f3 th\u1ec3 thay \u0111\u1ed5i ho\u1eb7c m\u1edf r\u1ed9ng (v\u00ed d\u1ee5: Tr\u1ea1ng th\u00e1i, Ti\u1ec1n t\u1ec7, Qu\u1ed1c gia).<\/li>\n
- Th\u1ef1c hi\u1ec7nR\u00e0ng bu\u1ed9c ki\u1ec3m tra<\/strong> \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o ch\u1ec9 c\u00f3 c\u00e1c gi\u00e1 tr\u1ecb h\u1ee3p l\u1ec7 \u0111\u01b0\u1ee3c nh\u1eadp, nh\u01b0ng gi\u1eef \u0111\u1ecbnh ngh\u0129a c\u1ee7a c\u00e1c gi\u00e1 tr\u1ecb \u0111\u00f3 trong \u1ee9ng d\u1ee5ng ho\u1eb7c trong m\u1ed9t b\u1ea3ng c\u1ea5u h\u00ecnh ri\u00eang bi\u1ec7t.<\/li>\n
- Ch\u1ec9 s\u1eed d\u1ee5ng ki\u1ec3u Enum n\u1ebfu h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u h\u1ed7 tr\u1ee3 ch\u00fang m\u1ed9t c\u00e1ch v\u1eefng ch\u1eafc v\u00e0 t\u1eadp h\u1ee3p gi\u00e1 tr\u1ecb th\u1ef1c s\u1ef1 c\u1ed1 \u0111\u1ecbnh.<\/li>\n
- T\u00e1ch d\u1eef li\u1ec7u c\u1ea5u h\u00ecnh kh\u1ecfi d\u1eef li\u1ec7u giao d\u1ecbch.<\/li>\n<\/ul>\n
7. B\u1ecf qua kh\u1ea3 n\u0103ng m\u1edf r\u1ed9ng trong t\u01b0\u01a1ng lai \ud83d\udcc8<\/h2>\n
Nhi\u1ec1u s\u01a1 \u0111\u1ed3 ERD \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf cho k\u00edch th\u01b0\u1edbc t\u1eadp d\u1eef li\u1ec7u hi\u1ec7n t\u1ea1i m\u00e0 kh\u00f4ng t\u00ednh \u0111\u1ebfn s\u1ef1 ph\u00e1t tri\u1ec3n. M\u1ed9t l\u01b0\u1ee3c \u0111\u1ed3 ho\u1ea1t \u0111\u1ed9ng t\u1ed1t v\u1edbi 1.000 b\u1ea3n ghi c\u00f3 th\u1ec3 th\u1ea5t b\u1ea1i nghi\u00eam tr\u1ecdng khi \u0111\u1ea1t \u0111\u1ebfn 10 tri\u1ec7u b\u1ea3n ghi do c\u00e1c v\u1ea5n \u0111\u1ec1 v\u1ec1 kh\u00f3a, ch\u1ec9 m\u1ee5c ho\u1eb7c chia t\u00e1ch d\u1eef li\u1ec7u.<\/p>\n
Nh\u1eefng sai l\u1ea7m v\u1ec1 kh\u1ea3 n\u0103ng m\u1edf r\u1ed9ng<\/h3>\n\n- C\u00e1c tr\u01b0\u1eddng v\u0103n b\u1ea3n l\u1edbn:<\/strong>L\u01b0u tr\u1eef c\u00e1c kh\u1ed1i d\u1eef li\u1ec7u l\u1edbn ho\u1eb7c chu\u1ed7i v\u0103n b\u1ea3n d\u00e0i trong b\u1ea3ng ch\u00ednh c\u00f3 th\u1ec3 l\u00e0m t\u0103ng k\u00edch th\u01b0\u1edbc ch\u1ec9 m\u1ee5c v\u00e0 l\u00e0m ch\u1eadm thao t\u00e1c \u0111\u1ecdc.<\/li>\n
- Thi\u1ebfu kh\u00f3a chia t\u00e1ch d\u1eef li\u1ec7u:<\/strong> N\u1ebfu l\u01b0\u1ee3c \u0111\u1ed3 kh\u00f4ng t\u00ednh \u0111\u1ebfn c\u00e1ch d\u1eef li\u1ec7u s\u1ebd \u0111\u01b0\u1ee3c chia nh\u1ecf ho\u1eb7c ph\u00e2n v\u00f9ng (v\u00ed d\u1ee5: theo ng\u00e0y ho\u1eb7c khu v\u1ef1c), vi\u1ec7c m\u1edf r\u1ed9ng ngang trong t\u01b0\u01a1ng lai s\u1ebd tr\u1edf th\u00e0nh m\u1ed9t thay \u0111\u1ed5i l\u1edbn.<\/li>\n
- Thi\u1ebfu ch\u1ec9 m\u1ee5c:<\/strong> Kh\u00f4ng l\u01b0\u1eddng tr\u01b0\u1edbc \u0111\u01b0\u1ee3c c\u00e1c c\u1ed9t n\u00e0o s\u1ebd \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 l\u1ecdc ho\u1eb7c s\u1eafp x\u1ebfp trong t\u01b0\u01a1ng lai d\u1eabn \u0111\u1ebfn c\u00e1c \u0111i\u1ec3m ngh\u1ebdn hi\u1ec7u su\u1ea5t.<\/li>\n
- M\u1eabu vi\u1ebft nhi\u1ec1u:<\/strong>M\u1ed9t thi\u1ebft k\u1ebf \u0111\u01b0\u1ee3c t\u1ed1i \u01b0u h\u00f3a cho thao t\u00e1c \u0111\u1ecdc c\u00f3 th\u1ec3 b\u1ecb ngh\u1ebdn khi th\u1ef1c hi\u1ec7n vi\u1ebft v\u1edbi kh\u1ed1i l\u01b0\u1ee3ng l\u1edbn do c\u01a1 ch\u1ebf kh\u00f3a tr\u00ean c\u00e1c kh\u00f3a ngo\u1ea1i.<\/li>\n<\/ul>\n
Thi\u1ebft k\u1ebf \u0111\u1ec3 ph\u00e1t tri\u1ec3n<\/h3>\n\n- Xem l\u1ea1i T\u1ef7 l\u1ec7 \u0111\u1ecdc\/vi\u1ebft<\/strong> c\u1ee7a \u1ee9ng d\u1ee5ng c\u1ee7a b\u1ea1n. N\u1ebfu n\u00f3 c\u00f3 xu h\u01b0\u1edbng vi\u1ebft nhi\u1ec1u, h\u00e3y t\u1ed1i thi\u1ec3u h\u00f3a c\u00e1c r\u00e0ng bu\u1ed9c kh\u00f3a ngo\u1ea1i g\u00e2y ra hi\u1ec7n t\u01b0\u1ee3ng kh\u00f3a.<\/li>\n
- Thi\u1ebft k\u1ebf Kh\u00f3a ph\u00e2n v\u00f9ng<\/strong> v\u00e0o s\u01a1 \u0111\u1ed3 ch\u00ednh c\u1ee7a b\u1ea1n. \u0110\u1ea3m b\u1ea3o m\u1ecdi b\u1ea3ng \u0111\u1ec1u c\u00f3 m\u1ed9t c\u1ed9t c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 chia d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch h\u1ee3p l\u00fd.<\/li>\n
- T\u00e1ch d\u1eef li\u1ec7u v\u0103n b\u1ea3n l\u1edbn v\u00e0o m\u1ed9t b\u1ea3ng ri\u00eang bi\u1ec7t (m\u1ed1i quan h\u1ec7 1:1) \u0111\u1ec3 gi\u1eef cho ch\u1ec9 m\u1ee5c ch\u00ednh lu\u00f4n g\u1ecdn nh\u1eb9.<\/li>\n
- L\u00ean k\u1ebf ho\u1ea1ch cho X\u00f3a m\u1ec1m<\/strong> thay v\u00ec x\u00f3a c\u1ee9ng \u0111\u1ec3 b\u1ea3o t\u1ed3n l\u1ecbch s\u1eed d\u1eef li\u1ec7u m\u00e0 kh\u00f4ng \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn hi\u1ec7u su\u1ea5t truy v\u1ea5n hi\u1ec7n t\u1ea1i.<\/li>\n<\/ul>\n
T\u00f3m t\u1eaft c\u00e1c th\u1ef1c h\u00e0nh t\u1ed1t nh\u1ea5t \ud83d\udccb<\/h2>\n
\u0110\u1ec3 \u0111\u1ea3m b\u1ea3o c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n lu\u00f4n \u1ed5n \u0111\u1ecbnh v\u00e0 d\u1ec5 b\u1ea3o tr\u00ec, h\u00e3y xem x\u00e9t s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 c\u1ee7a b\u1ea1n theo danh s\u00e1ch ki\u1ec3m tra sau tr\u01b0\u1edbc khi tri\u1ec3n khai.<\/p>\n
\n- Kh\u00f3a:<\/strong> M\u1ed7i b\u1ea3ng \u0111\u1ec1u c\u00f3 kh\u00f3a ch\u00ednh. C\u00e1c kh\u00f3a ngo\u1ea1i \u0111\u01b0\u1ee3c l\u1eadp ch\u1ec9 m\u1ee5c.<\/li>\n
- M\u1ed1i quan h\u1ec7:<\/strong> T\u00ednh cardinality \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh r\u00f5 r\u00e0ng. M\u1ed1i quan h\u1ec7 nhi\u1ec1u-nhi\u1ec1u s\u1eed d\u1ee5ng b\u1ea3ng li\u00ean k\u1ebft.<\/li>\n
- Chu\u1ea9n h\u00f3a:<\/strong> S\u1ef1 tr\u00f9ng l\u1eb7p d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c gi\u1ea3m thi\u1ec3u theo ti\u00eau chu\u1ea9n 3NF.<\/li>\n
- Ph\u1ee5 thu\u1ed9c:<\/strong> Kh\u00f4ng c\u00f3 v\u00f2ng l\u1eb7p kh\u00f3a ngo\u1ea1i v\u00f2ng m\u00e0 kh\u00f4ng c\u00f3 r\u00e0ng bu\u1ed9c ho\u00e3n l\u1ea1i.<\/li>\n
- \u0110\u1eb7t t\u00ean:<\/strong> S\u1eed d\u1ee5ng c\u00e1ch vi\u1ebft hoa nh\u1ea5t qu\u00e1n v\u00e0 t\u00ean m\u00f4 t\u1ea3 tr\u00ean to\u00e0n b\u1ed9 h\u1ec7 th\u1ed1ng.<\/li>\n
- Gi\u00e1 tr\u1ecb:<\/strong> Kh\u00f4ng c\u00f3 logic kinh doanh \u0111\u01b0\u1ee3c ghi c\u1ee9ng trong c\u1ea5u tr\u00fac l\u01b0\u1ee3c \u0111\u1ed3.<\/li>\n
- M\u1edf r\u1ed9ng:<\/strong> L\u01b0\u1ee3c \u0111\u1ed3 xem x\u00e9t c\u00e1c chi\u1ebfn l\u01b0\u1ee3c ph\u00e2n v\u00f9ng v\u00e0 l\u1eadp ch\u1ec9 m\u1ee5c \u0111\u1ec3 x\u1eed l\u00fd t\u1ea3i trong t\u01b0\u01a1ng lai.<\/li>\n<\/ul>\n
Suy ngh\u0129 cu\u1ed1i c\u00f9ng v\u1ec1 m\u00f4 h\u00ecnh h\u00f3a d\u1eef li\u1ec7u \ud83e\udde0<\/h2>\n
X\u00e2y d\u1ef1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u kh\u00f4ng ch\u1ec9 \u0111\u01a1n thu\u1ea7n l\u00e0 vi\u1ebftCREATE TABLE<\/code> c\u00e1c c\u00e2u l\u1ec7nh. \u0110\u00f3 l\u00e0 vi\u1ec7c m\u00f4 h\u00ecnh h\u00f3a th\u1ef1c t\u1ebf c\u1ee7a c\u00e1c quy tr\u00ecnh kinh doanh c\u1ee7a b\u1ea1n th\u00e0nh m\u1ed9t c\u1ea5u tr\u00fac logic m\u00e0 m\u00e1y t\u00ednh c\u00f3 th\u1ec3 x\u1eed l\u00fd m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3. Chi ph\u00ed s\u1eeda l\u1ed7i l\u01b0\u1ee3c \u0111\u1ed3 t\u0103ng theo c\u1ea5p s\u1ed1 nh\u00e2n n\u1ebfu ph\u00e1t hi\u1ec7n l\u1ed7i c\u00e0ng mu\u1ed9n trong chu k\u1ef3 ph\u00e1t tri\u1ec3n.<\/p>\nB\u1eb1ng c\u00e1ch tr\u00e1nh b\u1ea3y sai l\u1ea7m ph\u1ed5 bi\u1ebfn n\u00e0y, b\u1ea1n s\u1ebd gi\u1ea3m n\u1ee3 k\u1ef9 thu\u1eadt v\u00e0 t\u1ea1o n\u1ec1n t\u1ea3ng h\u1ed7 tr\u1ee3 c\u00e1c truy v\u1ea5n ph\u1ee9c t\u1ea1p v\u00e0 giao d\u1ecbch kh\u1ed1i l\u01b0\u1ee3ng l\u1edbn. H\u00e3y \u01b0u ti\u00ean s\u1ef1 r\u00f5 r\u00e0ng, t\u00ednh to\u00e0n v\u1eb9n v\u00e0 t\u00ednh linh ho\u1ea1t trong s\u01a1 \u0111\u1ed3 c\u1ee7a b\u1ea1n. M\u1ed9t s\u01a1 \u0111\u1ed3 ERD \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf t\u1ed1t s\u1ebd v\u00f4 h\u00ecnh v\u1edbi ng\u01b0\u1eddi d\u00f9ng cu\u1ed1i nh\u01b0ng l\u1ea1i thi\u1ebft y\u1ebfu cho s\u1ef1 b\u1ec1n v\u1eefng c\u1ee7a h\u1ec7 th\u1ed1ng.<\/p>\n
D\u00e0nh th\u1eddi gian xem x\u00e9t l\u1ea1i l\u01b0\u1ee3c \u0111\u1ed3 c\u1ee7a b\u1ea1n v\u1edbi c\u00e1i nh\u00ecn m\u1edbi m\u1ebb ho\u1eb7c th\u00f4ng qua quy tr\u00ecnh ki\u1ec3m tra b\u1edfi \u0111\u1ed3ng nghi\u1ec7p. \u0110\u1eb7t c\u00e2u h\u1ecfi v\u1ec1 l\u00fd do t\u1ea1i sao m\u1ed9t m\u1ed1i quan h\u1ec7 t\u1ed3n t\u1ea1i v\u00e0 n\u00f3 s\u1ebd ho\u1ea1t \u0111\u1ed9ng th\u1ebf n\u00e0o khi ch\u1ecbu t\u1ea3i. S\u1ef1 c\u1ea9n tr\u1ecdng n\u00e0y s\u1ebd mang l\u1ea1i l\u1ee3i \u00edch cho \u0111\u1ed9 tin c\u1eady c\u1ee7a h\u1ec7 th\u1ed1ng v\u00e0 n\u0103ng su\u1ea5t ph\u00e1t tri\u1ec3n c\u1ee7a nh\u00e0 ph\u00e1t tri\u1ec3n trong t\u01b0\u01a1ng lai.<\/p>\n","protected":false},"excerpt":{"rendered":"
Thi\u1ebft k\u1ebf m\u1ed9t c\u1ea5u tr\u00fac d\u1eef li\u1ec7u v\u1eefng ch\u1eafc l\u00e0 n\u1ec1n t\u1ea3ng c\u1ee7a b\u1ea5t k\u1ef3 h\u1ec7 th\u1ed1ng ph\u1ea7n m\u1ec1m \u0111\u00e1ng tin c\u1eady n\u00e0o. S\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 (ERD)…<\/p>\n","protected":false},"author":1,"featured_media":1604,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_yoast_wpseo_title":"7 Sai l\u1ea7m trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 khi\u1ebfn c\u01a1 s\u1edf d\u1eef li\u1ec7u b\u1ecb h\u1ecfng (v\u00e0 c\u00e1ch tr\u00e1nh ch\u00fang) \ud83d\udee0\ufe0f","_yoast_wpseo_metadesc":"Kh\u00e1m ph\u00e1 nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 l\u00e0m \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u. H\u1ecdc c\u00e1ch thi\u1ebft k\u1ebf c\u00e1c l\u01b0\u1ee3c \u0111\u1ed3 v\u1eefng ch\u1eafc v\u00e0 tr\u00e1nh vi\u1ec7c t\u00e1i c\u1ea5u tr\u00fac t\u1ed1n k\u00e9m.","fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[88],"tags":[84,87],"class_list":["post-1603","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-erd","tag-academic","tag-erd"],"yoast_head":"\n
7 Sai l\u1ea7m trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 khi\u1ebfn c\u01a1 s\u1edf d\u1eef li\u1ec7u b\u1ecb h\u1ecfng (v\u00e0 c\u00e1ch tr\u00e1nh ch\u00fang) \ud83d\udee0\ufe0f<\/title>\n<meta name=\"description\" content=\"Kh\u00e1m ph\u00e1 nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 l\u00e0m \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u. 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| Lo\u1ea1i quan h\u1ec7<\/th>\n | Chi\u1ebfn l\u01b0\u1ee3c tri\u1ec3n khai<\/th>\n | L\u1ed7i ph\u1ed5 bi\u1ebfn<\/th>\n<\/tr>\n<\/thead>\n |
|---|---|---|
| M\u1ed9t-\u0111\u1ed1i-m\u1ed9t<\/td>\n | Kh\u00f3a ngo\u1ea1i trong m\u1ed9t b\u1ea3ng v\u1edbi r\u00e0ng bu\u1ed9c UNIQUE<\/td>\n | Th\u00eam kh\u00f3a ngo\u1ea1i v\u00e0o c\u1ea3 hai b\u1ea3ng m\u1ed9t c\u00e1ch kh\u00f4ng c\u1ea7n thi\u1ebft<\/td>\n<\/tr>\n |
| M\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u<\/td>\n | Kh\u00f3a ngo\u1ea1i trong b\u1ea3ng \u201cNhi\u1ec1u\u201d<\/td>\n | L\u01b0u tr\u1eef d\u1eef li\u1ec7u cha trong b\u1ea3ng con (phi chu\u1ea9n h\u00f3a)<\/td>\n<\/tr>\n |
| Nhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u<\/td>\n | B\u1ea3ng li\u00ean k\u1ebft trung gian<\/td>\n | L\u01b0u tr\u1eef nhi\u1ec1u ID trong m\u1ed9t c\u1ed9t ph\u00e2n c\u00e1ch b\u1eb1ng d\u1ea5u ph\u1ea9y<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n3. B\u1ecf qua c\u00e1c ti\u00eau chu\u1ea9n chu\u1ea9n h\u00f3a \ud83d\udcc9<\/h2>\nChu\u1ea9n h\u00f3a l\u00e0 qu\u00e1 tr\u00ecnh t\u1ed5 ch\u1ee9c d\u1eef li\u1ec7u nh\u1eb1m gi\u1ea3m thi\u1ec3u s\u1ef1 tr\u00f9ng l\u1eb7p v\u00e0 c\u1ea3i thi\u1ec7n t\u00ednh to\u00e0n v\u1eb9n. Trong khi m\u1ed9t s\u1ed1 h\u1ec7 th\u1ed1ng hi\u1ec7n \u0111\u1ea1i ch\u1ea5p nh\u1eadn phi chu\u1ea9n h\u00f3a \u0111\u1ec3 t\u0103ng hi\u1ec7u su\u1ea5t \u0111\u1ecdc, nh\u01b0ng b\u1ecf qua ho\u00e0n to\u00e0n chu\u1ea9n h\u00f3a trong giai \u0111o\u1ea1n thi\u1ebft k\u1ebf s\u1ebd t\u1ea1o ra g\u00e1nh n\u1eb7ng b\u1ea3o tr\u00ec \u0111\u00e1ng k\u1ec3.<\/p>\n R\u1ee7i ro c\u1ee7a vi\u1ec7c chu\u1ea9n h\u00f3a k\u00e9m<\/h3>\nH\u01b0\u1edbng d\u1eabn tri\u1ec3n khai<\/h3>\n4. T\u1ea1o ra c\u00e1c ph\u1ee5 thu\u1ed9c v\u00f2ng l\u1eb7p \ud83d\udd01<\/h2>\nC\u00e1c ph\u1ee5 thu\u1ed9c v\u00f2ng x\u1ea3y ra khi c\u00e1c b\u1ea3ng tham chi\u1ebfu l\u1eabn nhau theo m\u1ed9t v\u00f2ng l\u1eb7p, ng\u0103n c\u1ea3n qu\u00e1 tr\u00ecnh kh\u1edfi t\u1ea1o ho\u1eb7c g\u00e2y ra \u0111\u1ec7 quy v\u00f4 h\u1ea1n trong truy v\u1ea5n. M\u1eb7c d\u00f9 c\u00e1c m\u1ed1i quan h\u1ec7 \u0111\u1ec7 quy (nh\u01b0 s\u01a1 \u0111\u1ed3 t\u1ed5 ch\u1ee9c n\u01a1i m\u1ed9t nh\u00e2n vi\u00ean c\u00f3 ng\u01b0\u1eddi qu\u1ea3n l\u00fd) l\u00e0 h\u1ee3p l\u1ec7, nh\u01b0ng c\u00e1c kh\u00f3a ngo\u1ea1i v\u00f2ng l\u1eb7p kh\u00f4ng ki\u1ec3m so\u00e1t \u0111\u01b0\u1ee3c c\u00f3 th\u1ec3 l\u00e0m h\u1ecfng c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/p>\n T\u1ea1i sao \u0111i\u1ec1u n\u00e0y l\u00e0m h\u1ecfng h\u1ec7 th\u1ed1ng<\/h3>\nC\u00e1ch kh\u1eafc ph\u1ee5c<\/h3>\n5. Quy \u01b0\u1edbc \u0111\u1eb7t t\u00ean kh\u00f4ng nh\u1ea5t qu\u00e1n \ud83d\udcdd<\/h2>\nT\u00ean l\u00e0 giao di\u1ec7n gi\u1eefa con ng\u01b0\u1eddi v\u00e0 m\u00e1y m\u00f3c. Vi\u1ec7c \u0111\u1eb7t t\u00ean kh\u00f4ng nh\u1ea5t qu\u00e1n trong t\u00ean b\u1ea3ng v\u00e0 c\u1ed9t khi\u1ebfn l\u01b0\u1ee3c \u0111\u1ed3 tr\u1edf n\u00ean kh\u00f3 hi\u1ec3u, kh\u00f3 b\u1ea3o tr\u00ec v\u00e0 truy v\u1ea5n. \u0110i\u1ec1u n\u00e0y th\u01b0\u1eddng xu\u1ea5t ph\u00e1t t\u1eeb vi\u1ec7c thi\u1ebfu m\u1ed9t h\u01b0\u1edbng d\u1eabn phong c\u00e1ch chung.<\/p>\n C\u00e1c v\u1ea5n \u0111\u1ec1 c\u1ee5 th\u1ec3<\/h3>\ncamelCase<\/code>, |