{"id":1577,"date":"2026-03-25T18:45:12","date_gmt":"2026-03-25T18:45:12","guid":{"rendered":"https:\/\/www.viz-read.com\/vi\/erd-troubleshooting-guide-fixing-broken-relationships\/"},"modified":"2026-03-25T18:45:12","modified_gmt":"2026-03-25T18:45:12","slug":"erd-troubleshooting-guide-fixing-broken-relationships","status":"publish","type":"post","link":"https:\/\/www.viz-read.com\/vi\/erd-troubleshooting-guide-fixing-broken-relationships\/","title":{"rendered":"H\u01b0\u1edbng d\u1eabn kh\u1eafc ph\u1ee5c s\u1ef1 c\u1ed1 ERD: S\u1eeda l\u1ed7i m\u1ed1i quan h\u1ec7 b\u1ecb h\u1ecfng tr\u01b0\u1edbc khi ch\u00fang g\u00e2y ra h\u1ed7n lo\u1ea1n"},"content":{"rendered":"

S\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 (ERD) \u0111\u00f3ng vai tr\u00f2 nh\u01b0 b\u1ea3n v\u1ebd thi\u1ebft k\u1ebf cho ki\u1ebfn tr\u00fac c\u01a1 s\u1edf d\u1eef li\u1ec7u. Ch\u00fang x\u00e1c \u0111\u1ecbnh c\u00e1ch d\u1eef li\u1ec7u k\u1ebft n\u1ed1i, c\u00e1ch duy tr\u00ec t\u00ednh to\u00e0n v\u1eb9n v\u00e0 c\u00e1ch th\u00f4ng tin l\u01b0u th\u00f4ng qua \u1ee9ng d\u1ee5ng. Khi c\u00e1c s\u01a1 \u0111\u1ed3 n\u00e0y ch\u1ee9a l\u1ed7i, h\u1ec7 qu\u1ea3 kh\u00f4ng ch\u1ec9 gi\u1edbi h\u1ea1n \u1edf h\u00ecnh \u1ea3nh tr\u1ef1c quan. Nh\u1eefng m\u1ed1i quan h\u1ec7 b\u1ecb h\u1ecfng c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn l\u1ed7i d\u1eef li\u1ec7u, \u1ee9ng d\u1ee5ng s\u1eadp v\u00e0 suy gi\u1ea3m hi\u1ec7u su\u1ea5t nghi\u00eam tr\u1ecdng. H\u01b0\u1edbng d\u1eabn n\u00e0y cung c\u1ea5p c\u00e1ch ti\u1ebfp c\u1eadn c\u00f3 c\u1ea5u tr\u00fac \u0111\u1ec3 x\u00e1c \u0111\u1ecbnh v\u00e0 kh\u1eafc ph\u1ee5c c\u00e1c v\u1ea5n \u0111\u1ec1 trong m\u00f4 h\u00ecnh d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n tr\u01b0\u1edbc khi ch\u00fang leo thang th\u00e0nh s\u1ef1 c\u1ed1 h\u1ec7 th\u1ed1ng nghi\u00eam tr\u1ecdng.<\/p>\n

Hi\u1ec3u r\u00f5 c\u01a1 ch\u1ebf ho\u1ea1t \u0111\u1ed9ng c\u1ee7a c\u00e1c m\u1ed1i quan h\u1ec7 l\u00e0 b\u01b0\u1edbc \u0111\u1ea7u ti\u00ean \u0111\u1ec3 t\u1ea1o n\u00ean m\u00f4i tr\u01b0\u1eddng \u1ed5n \u0111\u1ecbnh. Ch\u00fang ta s\u1ebd kh\u00e1m ph\u00e1 nh\u1eefng l\u1ed7i c\u1ea5u tr\u00fac ph\u1ed5 bi\u1ebfn, c\u00e1c ph\u01b0\u01a1ng ph\u00e1p ch\u1ea9n \u0111o\u00e1n v\u00e0 chi\u1ebfn l\u01b0\u1ee3c duy tr\u00ec s\u1ee9c kh\u1ecfe d\u1eef li\u1ec7u l\u00e2u d\u00e0i. B\u1eb1ng c\u00e1ch tu\u00e2n theo c\u00e1c quy tr\u00ecnh n\u00e0y, b\u1ea1n c\u00f3 th\u1ec3 \u0111\u1ea3m b\u1ea3o r\u1eb1ng l\u01b0\u1ee3c \u0111\u1ed3 c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a m\u00ecnh lu\u00f4n v\u1eefng ch\u1eafc v\u00e0 \u0111\u00e1ng tin c\u1eady.<\/p>\n

\n
\"Kawaii-style<\/figure>\n<\/div>\n

Hi\u1ec3u r\u00f5 t\u00ednh c\u1ea5p \u0111\u1ed9 quan h\u1ec7 \ud83d\udd17<\/h2>\n

\u1ede c\u1ed1t l\u00f5i c\u1ee7a b\u1ea5t k\u1ef3 s\u01a1 \u0111\u1ed3 ERD n\u00e0o l\u00e0 c\u00e1c m\u1ed1i quan h\u1ec7. Ch\u00fang x\u00e1c \u0111\u1ecbnh m\u1ed1i li\u00ean h\u1ec7 s\u1ed1 l\u01b0\u1ee3ng gi\u1eefa c\u00e1c th\u1ef1c th\u1ec3. Vi\u1ec7c hi\u1ec3u sai ho\u1eb7c c\u1ea5u h\u00ecnh sai c\u1ea5p \u0111\u1ed9 quan h\u1ec7 l\u00e0 nguy\u00ean nh\u00e2n ph\u1ed5 bi\u1ebfn d\u1eabn \u0111\u1ebfn s\u1ef1 kh\u00f4ng nh\u1ea5t qu\u00e1n d\u1eef li\u1ec7u. M\u1ed9t m\u1ed1i quan h\u1ec7 m\u00f4 t\u1ea3 c\u00e1ch c\u00e1c th\u1ec3 hi\u1ec7n c\u1ee7a m\u1ed9t th\u1ef1c th\u1ec3 li\u00ean k\u1ebft v\u1edbi c\u00e1c th\u1ec3 hi\u1ec7n c\u1ee7a th\u1ef1c th\u1ec3 kh\u00e1c. C\u00f3 ba lo\u1ea1i c\u1ea5p \u0111\u1ed9 quan h\u1ec7 ch\u00ednh c\u1ea7n \u0111\u01b0\u1ee3c tri\u1ec3n khai ch\u00ednh x\u00e1c.<\/p>\n

    \n
  • M\u1ed9t-\u0111\u1ed1i-m\u1ed9t (1:1):<\/strong> M\u1ed7i b\u1ea3n ghi trong Th\u1ef1c th\u1ec3 A li\u00ean k\u1ebft v\u1edbi \u0111\u00fang m\u1ed9t b\u1ea3n ghi trong Th\u1ef1c th\u1ec3 B. \u0110i\u1ec1u n\u00e0y ph\u1ed5 bi\u1ebfn trong c\u00e1c t\u00ecnh hu\u1ed1ng nh\u01b0 h\u1ed3 s\u01a1 ng\u01b0\u1eddi d\u00f9ng li\u00ean k\u1ebft v\u1edbi m\u00e3 x\u00e1c th\u1ef1c.<\/li>\n
  • M\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u (1:N):<\/strong> M\u1ed9t b\u1ea3n ghi duy nh\u1ea5t trong Th\u1ef1c th\u1ec3 A c\u00f3 th\u1ec3 li\u00ean k\u1ebft v\u1edbi nhi\u1ec1u b\u1ea3n ghi trong Th\u1ef1c th\u1ec3 B, nh\u01b0ng m\u1ed9t b\u1ea3n ghi trong Th\u1ef1c th\u1ec3 B ch\u1ec9 li\u00ean k\u1ebft v\u1edbi m\u1ed9t b\u1ea3n ghi duy nh\u1ea5t trong Th\u1ef1c th\u1ec3 A. \u0110\u00e2y l\u00e0 m\u1ed1i quan h\u1ec7 ph\u1ed5 bi\u1ebfn nh\u1ea5t, v\u00ed d\u1ee5 nh\u01b0 m\u1ed9t T\u00e1c gi\u1ea3 vi\u1ebft nhi\u1ec1u S\u00e1ch.<\/li>\n
  • Nhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u (M:N):<\/strong> C\u00e1c b\u1ea3n ghi trong Th\u1ef1c th\u1ec3 A c\u00f3 th\u1ec3 li\u00ean k\u1ebft v\u1edbi nhi\u1ec1u b\u1ea3n ghi trong Th\u1ef1c th\u1ec3 B, v\u00e0 ng\u01b0\u1ee3c l\u1ea1i. \u0110i\u1ec1u n\u00e0y \u0111\u00f2i h\u1ecfi m\u1ed9t b\u1ea3ng li\u00ean k\u1ebft trung gian \u0111\u1ec3 ho\u1ea1t \u0111\u1ed9ng \u0111\u00fang trong c\u00e1c c\u1ea5u tr\u00fac quan h\u1ec7.<\/li>\n<\/ul>\n

    Khi c\u00e1c c\u1ea5p \u0111\u1ed9 quan h\u1ec7 n\u00e0y \u0111\u01b0\u1ee3c \u0111\u1ecbnh ngh\u0129a sai trong s\u01a1 \u0111\u1ed3, l\u01b0\u1ee3c \u0111\u1ed3 c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u1eadt l\u00fd s\u1ebd ph\u1ea3n \u00e1nh nh\u1eefng l\u1ed7i \u0111\u00f3. V\u00ed d\u1ee5, \u0111\u1ecbnh ngh\u0129a m\u1ed1i quan h\u1ec7 1:1 th\u00e0nh 1:N m\u00e0 kh\u00f4ng c\u00f3 r\u00e0ng bu\u1ed9c duy nh\u1ea5t s\u1ebd cho ph\u00e9p c\u00e1c b\u1ea3n ghi tr\u00f9ng l\u1eb7p. Ng\u01b0\u1ee3c l\u1ea1i, \u00e9p bu\u1ed9c m\u1ed1i quan h\u1ec7 1:N th\u00e0nh 1:1 s\u1ebd ng\u0103n c\u1ea3n vi\u1ec7c m\u1edf r\u1ed9ng d\u1eef li\u1ec7u h\u1ee3p l\u1ec7. Vi\u1ec7c kh\u1eafc ph\u1ee5c s\u1ef1 c\u1ed1 b\u1eaft \u0111\u1ea7u b\u1eb1ng vi\u1ec7c x\u00e1c minh r\u1eb1ng s\u01a1 \u0111\u1ed3 tr\u1ef1c quan kh\u1edbp v\u1edbi c\u00e1c r\u00e0ng bu\u1ed9c logic mong mu\u1ed1n.<\/p>\n

    Nh\u1eefng l\u1ed7i c\u1ea5u tr\u00fac ph\u1ed5 bi\u1ebfn trong ERD \ud83d\udea8<\/h2>\n

    M\u1ed9t s\u1ed1 m\u1eabu l\u1ed7i c\u1ee5 th\u1ec3 th\u01b0\u1eddng xuy\u00ean xu\u1ea5t hi\u1ec7n trong c\u00e1c m\u00f4 h\u00ecnh d\u1eef li\u1ec7u. Vi\u1ec7c nh\u1eadn di\u1ec7n nh\u1eefng m\u1eabu n\u00e0y cho ph\u00e9p kh\u1eafc ph\u1ee5c c\u00f3 m\u1ee5c ti\u00eau. D\u01b0\u1edbi \u0111\u00e2y l\u00e0 ph\u00e2n t\u00edch c\u00e1c v\u1ea5n \u0111\u1ec1 ph\u1ed5 bi\u1ebfn nh\u1ea5t g\u1eb7p ph\u1ea3i trong qu\u00e1 tr\u00ecnh ki\u1ec3m to\u00e1n l\u01b0\u1ee3c \u0111\u1ed3.<\/p>\n

    1. Thi\u1ebfu r\u00e0ng bu\u1ed9c kh\u00f3a ngo\u1ea1i<\/h3>\n

    C\u00e1c s\u01a1 \u0111\u1ed3 tr\u1ef1c quan th\u01b0\u1eddng hi\u1ec3n th\u1ecb c\u00e1c \u0111\u01b0\u1eddng n\u1ed1i gi\u1eefa c\u00e1c b\u1ea3ng, nh\u01b0ng b\u1ed9 m\u00e1y c\u01a1 s\u1edf d\u1eef li\u1ec7u n\u1ec1n t\u1ea3ng c\u00f3 th\u1ec3 kh\u00f4ng th\u1ef1c thi nh\u1eefng k\u1ebft n\u1ed1i n\u00e0y. N\u1ebfu thi\u1ebfu r\u00e0ng bu\u1ed9c kh\u00f3a ngo\u1ea1i, c\u01a1 s\u1edf d\u1eef li\u1ec7u cho ph\u00e9p ‘b\u1ea3n ghi m\u1ed3 c\u00f4i’. \u0110\u00e2y l\u00e0 c\u00e1c b\u1ea3n ghi trong b\u1ea3ng con tham chi\u1ebfu \u0111\u1ebfn kh\u00f3a ch\u00ednh trong b\u1ea3ng cha m\u00e0 hi\u1ec7n kh\u00f4ng c\u00f2n t\u1ed3n t\u1ea1i ho\u1eb7c ch\u01b0a bao gi\u1edd \u0111\u01b0\u1ee3c t\u1ea1o. \u0110i\u1ec1u n\u00e0y l\u00e0m h\u1ecfng t\u00ednh to\u00e0n v\u1eb9n tham chi\u1ebfu.<\/p>\n

    2. Ph\u1ee5 thu\u1ed9c v\u00f2ng l\u1eb7p<\/h3>\n

    M\u1ed9t tham chi\u1ebfu v\u00f2ng x\u1ea3y ra khi Th\u1ef1c th\u1ec3 A ph\u1ee5 thu\u1ed9c v\u00e0o Th\u1ef1c th\u1ec3 B, v\u00e0 Th\u1ef1c th\u1ec3 B ph\u1ee5 thu\u1ed9c v\u00e0o Th\u1ef1c th\u1ec3 A. M\u1eb7c d\u00f9 \u0111\u00f4i khi l\u00e0 c\u1ea7n thi\u1ebft, \u0111i\u1ec1u n\u00e0y t\u1ea1o ra t\u00ecnh tr\u1ea1ng k\u1eb9t trong qu\u00e1 tr\u00ecnh kh\u1edfi t\u1ea1o. H\u1ec7 th\u1ed1ng kh\u00f4ng th\u1ec3 t\u1ea1o A m\u00e0 kh\u00f4ng c\u00f3 B, v\u00e0 c\u0169ng kh\u00f4ng th\u1ec3 t\u1ea1o B m\u00e0 kh\u00f4ng c\u00f3 A. \u0110i\u1ec1u n\u00e0y \u0111\u00f2i h\u1ecfi ph\u1ea3i ph\u00e1 v\u1ee1 v\u00f2ng l\u1eb7p b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng c\u00e1c c\u1ed9t c\u00f3 th\u1ec3 null ho\u1eb7c c\u00e1c t\u1eadp l\u1ec7nh kh\u1edfi t\u1ea1o x\u1eed l\u00fd th\u1ee9 t\u1ef1 ph\u1ee5 thu\u1ed9c.<\/p>\n

    3. Sai l\u1ec7ch ki\u1ec3u d\u1eef li\u1ec7u<\/h3>\n

    C\u00e1c m\u1ed1i quan h\u1ec7 ph\u1ee5 thu\u1ed9c v\u00e0o ki\u1ec3u d\u1eef li\u1ec7u kh\u1edbp nhau. N\u1ebfu kh\u00f3a ch\u00ednh trong m\u1ed9t b\u1ea3ng l\u00e0 ki\u1ec3u Integer, th\u00ec kh\u00f3a ngo\u1ea1i trong b\u1ea3ng li\u00ean quan c\u0169ng ph\u1ea3i l\u00e0 ki\u1ec3u Integer. S\u1ef1 sai l\u1ec7ch gi\u1eefa s\u1ed1 nguy\u00ean c\u00f3 d\u1ea5u v\u00e0 kh\u00f4ng d\u1ea5u, ho\u1eb7c gi\u1eefa chu\u1ed7i v\u00e0 s\u1ed1, s\u1ebd khi\u1ebfn c\u00e1c thao t\u00e1c n\u1ed1i (join) th\u1ea5t b\u1ea1i ho\u1eb7c ho\u1ea1t \u0111\u1ed9ng kh\u00f4ng nh\u01b0 mong \u0111\u1ee3i. \u0110i\u1ec1u n\u00e0y th\u01b0\u1eddng x\u1ea3y ra khi nh\u1eadp d\u1eef li\u1ec7u c\u0169 ho\u1eb7c trong qu\u00e1 tr\u00ecnh di chuy\u1ec3n l\u01b0\u1ee3c \u0111\u1ed3.<\/p>\n

    4. Sai l\u1ec7ch t\u00ednh kh\u1ea3 d\u1ee5ng null<\/h3>\n

    C\u00e1c c\u1ed9t kh\u00f3a ngo\u1ea1i x\u00e1c \u0111\u1ecbnh m\u1ed1i quan h\u1ec7 l\u00e0 b\u1eaft bu\u1ed9c hay t\u00f9y ch\u1ecdn. N\u1ebfu m\u1ed1i quan h\u1ec7 \u0111\u01b0\u1ee3c \u0111\u00e1nh d\u1ea5u l\u00e0 b\u1eaft bu\u1ed9c trong s\u01a1 \u0111\u1ed3, c\u1ed9t \u0111\u00f3 kh\u00f4ng \u0111\u01b0\u1ee3c ch\u1ea5p nh\u1eadn gi\u00e1 tr\u1ecb NULL. Cho ph\u00e9p NULL \u1edf n\u01a1i m\u1ed1i quan h\u1ec7 b\u1eaft bu\u1ed9c c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn t\u1eadp d\u1eef li\u1ec7u kh\u00f4ng \u0111\u1ea7y \u0111\u1ee7. Ng\u01b0\u1ee3c l\u1ea1i, ng\u0103n c\u1ea3n NULL \u1edf n\u01a1i m\u1ed1i quan h\u1ec7 l\u00e0 t\u00f9y ch\u1ecdn s\u1ebd bu\u1ed9c l\u1ed7i nh\u1eadp d\u1eef li\u1ec7u.<\/p>\n\n\n\n\n\n\n\n\n
    Lo\u1ea1i l\u1ed7i<\/th>\nT\u00e1c \u0111\u1ed9ng<\/th>\nTri\u1ec7u ch\u1ee9ng \u0111i\u1ec3n h\u00ecnh<\/th>\n<\/tr>\n<\/thead>\n
    Thi\u1ebfu kh\u00f3a ngo\u1ea1i<\/td>\nM\u1ea5t t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u<\/td>\nC\u00e1c b\u1ea3n ghi m\u1ed3 c\u00f4i v\u1eabn t\u1ed3n t\u1ea1i sau khi x\u00f3a b\u1ea3n cha<\/td>\n<\/tr>\n
    C\u1ea5p \u0111\u1ed9 quan h\u1ec7 sai<\/td>\nS\u1ef1 kh\u00f4ng nh\u1ea5t qu\u00e1n v\u1ec1 m\u1eb7t logic<\/td>\nC\u00e1c truy v\u1ea5n tr\u1ea3 v\u1ec1 d\u1eef li\u1ec7u li\u00ean quan b\u1ecb tr\u00f9ng l\u1eb7p ho\u1eb7c thi\u1ebfu<\/td>\n<\/tr>\n
    Sai ki\u1ec3u d\u1eef li\u1ec7u<\/td>\nTh\u1ea5t b\u1ea1i khi k\u1ebft n\u1ed1i<\/td>\nL\u1ed7i SQL ho\u1eb7c t\u1eadp k\u1ebft qu\u1ea3 tr\u1ed1ng tr\u00ean c\u00e1c m\u1ed1i quan h\u1ec7<\/td>\n<\/tr>\n
    Tham chi\u1ebfu v\u00f2ng<\/td>\nTh\u1ea5t b\u1ea1i kh\u1edfi t\u1ea1o<\/td>\nC\u00e1c t\u1eadp l\u1ec7nh t\u1ea1o c\u01a1 s\u1edf d\u1eef li\u1ec7u b\u1ecb d\u1eebng ho\u1eb7c h\u1ebft th\u1eddi gian<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    C\u00e1c b\u01b0\u1edbc ch\u1ea9n \u0111o\u00e1n \u0111\u1ec3 ph\u00e2n t\u00edch l\u01b0\u1ee3c \u0111\u1ed3 \ud83d\udd0d<\/h2>\n

    Vi\u1ec7c gi\u1ea3i quy\u1ebft c\u00e1c v\u1ea5n \u0111\u1ec1 ERD \u0111\u00f2i h\u1ecfi ph\u01b0\u01a1ng ph\u00e1p h\u1ec7 th\u1ed1ng. \u0110o\u00e1n m\u00f2 v\u1ec1 gi\u1ea3i ph\u00e1p th\u01b0\u1eddng d\u1eabn \u0111\u1ebfn c\u00e1c l\u1ed7i m\u1edbi. H\u00e3y tu\u00e2n theo tr\u00ecnh t\u1ef1 n\u00e0y \u0111\u1ec3 c\u00f4 l\u1eadp v\u00e0 kh\u1eafc ph\u1ee5c c\u00e1c v\u1ea5n \u0111\u1ec1 v\u1ec1 m\u1ed1i quan h\u1ec7.<\/p>\n

    B\u01b0\u1edbc 1: Ki\u1ec3m tra tr\u1ef1c quan<\/h3>\n

    B\u1eaft \u0111\u1ea7u b\u1eb1ng c\u00e1ch xem x\u00e9t s\u01a1 \u0111\u1ed3 theo y\u00eau c\u1ea7u kinh doanh. \u0110\u1ea3m b\u1ea3o m\u1ecdi \u0111\u01b0\u1eddng k\u1ebb th\u1ec3 hi\u1ec7n nhu c\u1ea7u d\u1eef li\u1ec7u th\u1ef1c t\u1ebf. Lo\u1ea1i b\u1ecf c\u00e1c \u0111\u01b0\u1eddng trang tr\u00ed ho\u1eb7c suy di\u1ec5n kh\u00f4ng t\u1ed3n t\u1ea1i trong l\u01b0\u1ee3c \u0111\u1ed3 v\u1eadt l\u00fd. T\u00ecm c\u00e1c b\u1ea3ng li\u00ean k\u1ebft trong c\u00e1c m\u1ed1i quan h\u1ec7 Nhi\u1ec1u-\u0110a; ch\u00fang kh\u00f4ng \u0111\u01b0\u1ee3c b\u1ecf qua.<\/p>\n

    B\u01b0\u1edbc 2: Ph\u00e2n t\u00edch truy v\u1ea5n<\/h3>\n

    Xem x\u00e9t \u0111\u1ecbnh ngh\u0129a l\u01b0\u1ee3c \u0111\u1ed3 SQL th\u1ef1c t\u1ebf. So s\u00e1nh c\u00e1c c\u00e2u l\u1ec7nh CREATE v\u1edbi m\u00f4 h\u00ecnh tr\u1ef1c quan. Ki\u1ec3m tra nh\u1eefng \u0111i\u1ec1u sau:<\/p>\n

      \n
    • T\u1ea5t c\u1ea3 c\u00e1c kh\u00f3a ngo\u1ea1i c\u00f3 t\u1ed3n t\u1ea1i trong t\u1eeb \u0111i\u1ec3n d\u1eef li\u1ec7u kh\u00f4ng?<\/li>\n
    • C\u00e1c t\u00ean c\u1ed9t c\u00f3 nh\u1ea5t qu\u00e1n gi\u1eefa b\u1ea3ng cha v\u00e0 b\u1ea3ng con kh\u00f4ng?<\/li>\n
    • Ch\u1ec9 m\u1ee5c tr\u00ean c\u1ed9t kh\u00f3a ngo\u1ea1i c\u00f3 t\u1ed3n t\u1ea1i kh\u00f4ng? Thi\u1ebfu ch\u1ec9 m\u1ee5c l\u00e0m ch\u1eadm \u0111\u00e1ng k\u1ec3 c\u00e1c truy v\u1ea5n li\u00ean quan.<\/li>\n<\/ul>\n

      B\u01b0\u1edbc 3: X\u00e1c th\u1ef1c r\u00e0ng bu\u1ed9c<\/h3>\n

      Ch\u1ea1y c\u00e1c truy v\u1ea5n \u0111\u1ec3 ki\u1ec3m tra t\u00ednh to\u00e0n v\u1eb9n tham chi\u1ebfu. Th\u1eed x\u00f3a m\u1ed9t b\u1ea3n ghi cha v\u00e0 quan s\u00e1t xem h\u1ec7 th\u1ed1ng c\u00f3 ng\u0103n ch\u1eb7n (T\u1ef1 \u0111\u1ed9ng x\u00f3a theo) hay cho ph\u00e9p (B\u1ecf qua). \u0110i\u1ec1u n\u00e0y x\u00e1c nh\u1eadn r\u00e0ng bu\u1ed9c c\u00f3 \u0111ang ho\u1ea1t \u0111\u1ed9ng hay kh\u00f4ng. Ki\u1ec3m tra c\u00e1c trigger c\u00f3 th\u1ec3 ghi \u0111\u00e8 h\u00e0nh vi m\u1eb7c \u0111\u1ecbnh c\u1ee7a r\u00e0ng bu\u1ed9c.<\/p>\n

      B\u01b0\u1edbc 4: Ph\u00e2n t\u00edch d\u1eef li\u1ec7u<\/h3>\n

      Ph\u00e2n t\u00edch d\u1eef li\u1ec7u th\u1ef1c t\u1ebf \u0111\u01b0\u1ee3c l\u01b0u trong c\u00e1c b\u1ea3ng. \u0110\u1ebfm s\u1ed1 b\u1ea3n ghi trong b\u1ea3ng con m\u00e0 gi\u00e1 tr\u1ecb kh\u00f3a ngo\u1ea1i kh\u00f4ng t\u1ed3n t\u1ea1i trong b\u1ea3ng cha. \u0110i\u1ec1u n\u00e0y gi\u00fap \u0111\u1ecbnh l\u01b0\u1ee3ng m\u1ee9c \u0111\u1ed9 t\u1ed5n h\u1ea1i do thi\u1ebfu r\u00e0ng bu\u1ed9c. M\u1ed9t con s\u1ed1 l\u1edbn h\u01a1n kh\u00f4ng cho th\u1ea5y s\u1ef1 vi ph\u1ea1m t\u00ednh to\u00e0n v\u1eb9n c\u1ea7n \u0111\u01b0\u1ee3c l\u00e0m s\u1ea1ch.<\/p>\n

      X\u1eed l\u00fd c\u00e1c b\u1ea3n ghi m\u1ed3 c\u00f4i v\u00e0 r\u00e0ng bu\u1ed9c \ud83d\udee1\ufe0f<\/h2>\n

      C\u00e1c b\u1ea3n ghi m\u1ed3 c\u00f4i l\u00e0 d\u1ea5u hi\u1ec7u r\u00f5 r\u00e0ng nh\u1ea5t c\u1ee7a m\u1ed1i quan h\u1ec7 b\u1ecb h\u1ecfng. Ch\u00fang x\u1ea3y ra khi b\u1ea3n ghi cha b\u1ecb x\u00f3a nh\u01b0ng c\u00e1c b\u1ea3n ghi con v\u1eabn t\u1ed3n t\u1ea1i. C\u00e1ch b\u1ea1n x\u1eed l\u00fd ph\u1ee5 thu\u1ed9c v\u00e0o logic kinh doanh. C\u00f3 ba c\u00e1ch chu\u1ea9n \u0111\u1ec3 qu\u1ea3n l\u00fd vi\u1ec7c x\u00f3a trong m\u00f4 h\u00ecnh quan h\u1ec7.<\/p>\n

        \n
      • X\u00f3a theo c\u1ea5p (Cascade Delete):<\/strong> Khi b\u1ea3n ghi cha b\u1ecb x\u00f3a, t\u1ea5t c\u1ea3 c\u00e1c b\u1ea3n ghi con li\u00ean quan s\u1ebd b\u1ecb x\u00f3a t\u1ef1 \u0111\u1ed9ng. \u0110i\u1ec1u n\u00e0y \u0111\u1ea3m b\u1ea3o kh\u00f4ng c\u00f2n d\u1eef li\u1ec7u m\u1ed3 c\u00f4i n\u00e0o t\u1ed3n t\u1ea1i, nh\u01b0ng l\u1ea1i ti\u1ec1m \u1ea9n nguy c\u01a1 m\u1ea5t th\u00f4ng tin c\u00f3 th\u1ec3 v\u1eabn c\u1ea7n thi\u1ebft cho c\u00e1c b\u1ea3n ghi ki\u1ec3m to\u00e1n.<\/li>\n
      • H\u1ea1n ch\u1ebf x\u00f3a:<\/strong> H\u1ec7 th\u1ed1ng ng\u0103n vi\u1ec7c x\u00f3a b\u1ea3n ghi cha n\u1ebfu t\u1ed3n t\u1ea1i b\u1ea3n ghi con. \u0110i\u1ec1u n\u00e0y bu\u1ed9c qu\u1ea3n tr\u1ecb vi\u00ean ph\u1ea3i x\u1eed l\u00fd c\u00e1c b\u1ea3n ghi con tr\u01b0\u1edbc. \u0110\u00e2y l\u00e0 l\u1ef1a ch\u1ecdn an to\u00e0n nh\u1ea5t \u0111\u1ec3 b\u1ea3o t\u1ed3n d\u1eef li\u1ec7u.<\/li>\n
      • Thi\u1ebft l\u1eadp gi\u00e1 tr\u1ecb NULL:<\/strong> Khi b\u1ea3n ghi cha b\u1ecb x\u00f3a, kh\u00f3a ngo\u1ea1i trong c\u00e1c b\u1ea3n ghi con s\u1ebd \u0111\u01b0\u1ee3c thi\u1ebft l\u1eadp th\u00e0nh NULL. \u0110i\u1ec1u n\u00e0y gi\u1eef nguy\u00ean c\u00e1c b\u1ea3n ghi con nh\u01b0ng ph\u00e1 v\u1ee1 li\u00ean k\u1ebft m\u1ed1i quan h\u1ec7.<\/li>\n<\/ul>\n

        Khi kh\u1eafc ph\u1ee5c s\u1ef1 c\u1ed1, b\u1ea1n ph\u1ea3i quy\u1ebft \u0111\u1ecbnh h\u00e0nh vi n\u00e0o ph\u00f9 h\u1ee3p v\u1edbi y\u00eau c\u1ea7u c\u1ee7a m\u00ecnh. N\u1ebfu s\u01a1 \u0111\u1ed3 c\u1ee7a b\u1ea1n ng\u1ee5 \u00fd m\u1ed9t c\u1ea5u tr\u00fac ph\u00e2n c\u1ea5p nghi\u00eam ng\u1eb7t nh\u01b0ng c\u01a1 s\u1edf d\u1eef li\u1ec7u cho ph\u00e9p thi\u1ebft l\u1eadp NULL, b\u1ea1n \u0111ang g\u1eb7p s\u1ef1 b\u1ea5t nh\u1ea5t. Vi\u1ec7c kh\u1eafc ph\u1ee5c \u0111i\u1ec1u n\u00e0y \u0111\u00f2i h\u1ecfi thay \u0111\u1ed5i r\u00e0ng bu\u1ed9c b\u1ea3ng. H\u00e3y c\u1ea9n tr\u1ecdng khi thay \u0111\u1ed5i r\u00e0ng bu\u1ed9c tr\u00ean c\u00e1c b\u1ea3ng \u0111\u00e3 c\u00f3 d\u1eef li\u1ec7u; b\u1ea1n c\u00f3 th\u1ec3 c\u1ea7n l\u00e0m s\u1ea1ch d\u1eef li\u1ec7u tr\u01b0\u1edbc \u0111\u1ec3 tr\u00e1nh vi ph\u1ea1m r\u00e0ng bu\u1ed9c.<\/p>\n

        Ng\u0103n ch\u1eb7n s\u1ef1 l\u1ec7ch l\u1ea1c d\u1eef li\u1ec7u<\/h3>\n

        S\u1ef1 l\u1ec7ch chu\u1ea9n x\u1ea3y ra khi c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u1eadt l\u00fd thay \u0111\u1ed5i m\u00e0 kh\u00f4ng c\u1eadp nh\u1eadt s\u01a1 \u0111\u1ed3. \u0110\u1ec3 ng\u0103n ch\u1eb7n \u0111i\u1ec1u n\u00e0y:<\/p>\n

          \n
        • Th\u1ef1c hi\u1ec7n ki\u1ec3m so\u00e1t phi\u00ean b\u1ea3n cho c\u00e1c \u0111\u1ecbnh ngh\u0129a l\u01b0\u1ee3c \u0111\u1ed3.<\/li>\n
        • S\u1eed d\u1ee5ng c\u00e1c t\u1eadp l\u1ec7nh di chuy\u1ec3n ghi l\u1ea1i m\u1ecdi thay \u0111\u1ed5i.<\/li>\n
        • Th\u1ef1c hi\u1ec7n ki\u1ec3m to\u00e1n \u0111\u1ecbnh k\u1ef3, trong \u0111\u00f3 s\u01a1 \u0111\u1ed3 \u0111\u01b0\u1ee3c so s\u00e1nh v\u1edbi l\u01b0\u1ee3c \u0111\u1ed3 c\u01a1 s\u1edf d\u1eef li\u1ec7u \u0111ang ho\u1ea1t \u0111\u1ed9ng.<\/li>\n
        • T\u00e0i li\u1ec7u l\u00fd do \u0111\u1eb1ng sau m\u1ecdi thay \u0111\u1ed5i m\u1ed1i quan h\u1ec7 trong l\u1ecbch s\u1eed d\u1ef1 \u00e1n.<\/li>\n<\/ul>\n

          T\u00e1c \u0111\u1ed9ng hi\u1ec7u su\u1ea5t c\u1ee7a thi\u1ebft k\u1ebf k\u00e9m \u26a1<\/h2>\n

          L\u1ed7i m\u1ed1i quan h\u1ec7 kh\u00f4ng ch\u1ec9 g\u00e2y ra v\u1ea5n \u0111\u1ec1 d\u1eef li\u1ec7u; ch\u00fang c\u00f2n \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn t\u1ed1c \u0111\u1ed9. B\u1ed9 x\u1eed l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u ph\u1ee5 thu\u1ed9c v\u00e0o ch\u1ec9 m\u1ee5c v\u00e0 r\u00e0ng bu\u1ed9c \u0111\u1ec3 t\u1ed1i \u01b0u h\u00f3a c\u00e1c thao t\u00e1c n\u1ed1i. Khi c\u00e1c m\u1ed1i quan h\u1ec7 \u0111\u01b0\u1ee3c \u0111\u1ecbnh ngh\u0129a k\u00e9m, b\u1ed9 x\u1eed l\u00fd ph\u1ea3i th\u1ef1c hi\u1ec7n qu\u00e9t to\u00e0n b\u1ed9 b\u1ea3ng thay v\u00ec s\u1eed d\u1ee5ng tra c\u1ee9u ch\u1ec9 m\u1ee5c.<\/p>\n

          \u0110\u1ed9 ph\u1ee9c t\u1ea1p c\u1ee7a thao t\u00e1c n\u1ed1i<\/h3>\n

          M\u1ed9t m\u1ed1i quan h\u1ec7 Nhi\u1ec1u-\u0110a nhi\u1ec1u ph\u1ee9c t\u1ea1p m\u00e0 kh\u00f4ng c\u00f3 ch\u1ec9 m\u1ee5c ph\u00f9 h\u1ee3p tr\u00ean b\u1ea3ng giao nhau c\u00f3 th\u1ec3 l\u00e0m ch\u1eadm truy v\u1ea5n theo c\u1ea5p s\u1ed1 nh\u00e2n. Khi d\u1eef li\u1ec7u t\u0103ng l\u00ean, s\u1ed1 l\u01b0\u1ee3ng t\u1ed5 h\u1ee3p c\u0169ng t\u0103ng theo. N\u1ebfu c\u00e1c kh\u00f3a ngo\u1ea1i trong b\u1ea3ng giao nhau kh\u00f4ng \u0111\u01b0\u1ee3c ch\u1ec9 m\u1ee5c, c\u01a1 s\u1edf d\u1eef li\u1ec7u kh\u00f4ng th\u1ec3 nhanh ch\u00f3ng t\u00ecm th\u1ea5y c\u00e1c h\u00e0ng li\u00ean quan. \u0110i\u1ec1u n\u00e0y d\u1eabn \u0111\u1ebfn s\u1eed d\u1ee5ng CPU cao v\u00e0 th\u1eddi gian ph\u1ea3n h\u1ed3i ch\u1eadm cho ng\u01b0\u1eddi d\u00f9ng.<\/p>\n

          Xung \u0111\u1ed9t kh\u00f3a<\/h3>\n

          C\u00e1c \u0111\u1ecbnh ngh\u0129a r\u00e0ng bu\u1ed9c sai c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn vi\u1ec7c kh\u00f3a qu\u00e1 m\u1ee9c. N\u1ebfu thao t\u00e1c x\u00f3a k\u00edch ho\u1ea1t thao t\u00e1c lan truy\u1ec1n qua m\u1ed9t b\u1ea3ng l\u1edbn, h\u1ec7 th\u1ed1ng c\u00f3 th\u1ec3 kh\u00f3a c\u00e1c h\u00e0ng trong th\u1eddi gian d\u00e0i. \u0110i\u1ec1u n\u00e0y ng\u0103n c\u1ea3n ng\u01b0\u1eddi d\u00f9ng kh\u00e1c truy c\u1eadp d\u1eef li\u1ec7u. Vi\u1ec7c kh\u1eafc ph\u1ee5c c\u00e1c v\u1ea5n \u0111\u1ec1 hi\u1ec7u su\u1ea5t th\u01b0\u1eddng \u0111\u00f2i h\u1ecfi xem x\u00e9t l\u1ea1i c\u00e1c r\u00e0ng bu\u1ed9c m\u1ed1i quan h\u1ec7 \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o ch\u00fang kh\u00f4ng g\u00e2y ra c\u00e1c kh\u00f3a c\u1ea5p h\u00e0ng kh\u00f4ng c\u1ea7n thi\u1ebft.<\/p>\n

          T\u1ed1i \u01b0u h\u00f3a truy v\u1ea5n<\/h3>\n

          C\u00e1c truy v\u1ea5n \u0111\u01b0\u1ee3c t\u1ed1i \u01b0u h\u00f3a ph\u1ee5 thu\u1ed9c v\u00e0o vi\u1ec7c bi\u1ebft \u0111\u01b0\u1ee3c m\u1ee9c \u0111\u1ed9 m\u1ea1nh c\u1ee7a m\u1ed1i quan h\u1ec7. N\u1ebfu b\u1ed9 t\u1ed1i \u01b0u h\u00f3a cho r\u1eb1ng m\u1ed1i quan h\u1ec7 l\u00e0 m\u1ed9t-\u0111\u1ed1i-m\u1ed9t nh\u01b0ng th\u1ef1c t\u1ebf l\u00e0 m\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u, n\u00f3 c\u00f3 th\u1ec3 ch\u1ecdn m\u1ed9t k\u1ebf ho\u1ea1ch th\u1ef1c thi kh\u00f4ng t\u1ed1i \u01b0u. \u0110i\u1ec1u n\u00e0y d\u1eabn \u0111\u1ebfn vi\u1ec7c t\u1ea1o ra c\u00e1c b\u1ea3ng t\u1ea1m ho\u1eb7c s\u1eafp x\u1ebfp kh\u00f4ng c\u1ea7n thi\u1ebft trong k\u1ebf ho\u1ea1ch th\u1ef1c thi truy v\u1ea5n. Vi\u1ec7c ph\u00e2n t\u00edch hi\u1ec7u su\u1ea5t truy v\u1ea5n \u0111\u1ecbnh k\u1ef3 c\u00f3 th\u1ec3 ti\u1ebft l\u1ed9 n\u01a1i d\u1eef li\u1ec7u m\u00f4 t\u1ea3 m\u1ed1i quan h\u1ec7 \u0111ang g\u00e2y hi\u1ec3u l\u1ea7m cho b\u1ed9 x\u1eed l\u00fd.<\/p>\n

          Chi\u1ebfn l\u01b0\u1ee3c b\u1ea3o tr\u00ec v\u00e0 ph\u00f2ng ng\u1eeba \ud83d\udee0\ufe0f<\/h2>\n

          Sau khi c\u00e1c v\u1ea5n \u0111\u1ec1 c\u1ea5p b\u00e1ch \u0111\u01b0\u1ee3c gi\u1ea3i quy\u1ebft, tr\u1ecdng t\u00e2m chuy\u1ec3n sang ph\u00f2ng ng\u1eeba. M\u1ed9t s\u01a1 \u0111\u1ed3 ERD m\u1ea1nh m\u1ebd kh\u00f4ng ph\u1ea3i l\u00e0 m\u1ed9t c\u00f4ng vi\u1ec7c m\u1ed9t l\u1ea7n; n\u00f3 \u0111\u00f2i h\u1ecfi b\u1ea3o tr\u00ec li\u00ean t\u1ee5c. C\u00e1c th\u1ef1c h\u00e0nh sau \u0111\u00e2y gi\u00fap duy tr\u00ec s\u1ee9c kh\u1ecfe d\u1eef li\u1ec7u theo th\u1eddi gian.<\/p>\n

            \n
          • Ti\u00eau chu\u1ea9n h\u00f3a quy \u01b0\u1edbc \u0111\u1eb7t t\u00ean:<\/strong> \u0110\u1ea3m b\u1ea3o c\u00e1c c\u1ed9t kh\u00f3a ngo\u1ea1i tu\u00e2n theo m\u1eabu \u0111\u1eb7t t\u00ean nh\u1ea5t qu\u00e1n (v\u00ed d\u1ee5, parent_id<\/code>). \u0110i\u1ec1u n\u00e0y gi\u00fap d\u1ec5 d\u00e0ng ph\u00e1t hi\u1ec7n c\u00e1c m\u1ed1i quan h\u1ec7 b\u1ecb thi\u1ebfu trong qu\u00e1 tr\u00ecnh ki\u1ec3m tra m\u00e3 ngu\u1ed3n.<\/li>\n
          • X\u00e1c th\u1ef1c l\u01b0\u1ee3c \u0111\u1ed3 t\u1ef1 \u0111\u1ed9ng:<\/strong> T\u00edch h\u1ee3p x\u00e1c th\u1ef1c l\u01b0\u1ee3c \u0111\u1ed3 v\u00e0o pipeline CI\/CD. N\u1ebfu m\u1ed9t nh\u00e0 ph\u00e1t tri\u1ec3n c\u1ed1 g\u1eafng tri\u1ec3n khai thay \u0111\u1ed5i l\u01b0\u1ee3c \u0111\u1ed3 vi ph\u1ea1m quy t\u1eafc b\u1ed9i s\u1ed1, qu\u00e1 tr\u00ecnh x\u00e2y d\u1ef1ng ph\u1ea3i th\u1ea5t b\u1ea1i.<\/li>\n
          • Sao l\u01b0u \u0111\u1ecbnh k\u1ef3:<\/strong> Tr\u01b0\u1edbc khi th\u1ef1c hi\u1ec7n thay \u0111\u1ed5i c\u1ea5u tr\u00fac, lu\u00f4n sao l\u01b0u c\u01a1 s\u1edf d\u1eef li\u1ec7u. \u0110i\u1ec1u n\u00e0y t\u1ea1o ra m\u1ed9t l\u1edbp an to\u00e0n n\u1ebfu vi\u1ec7c s\u1eeda ch\u1eefa r\u00e0ng bu\u1ed9c l\u00e0m h\u1ecfng d\u1eef li\u1ec7u.<\/li>\n
          • C\u1eadp nh\u1eadt t\u00e0i li\u1ec7u:<\/strong> M\u1ed7i khi m\u1ed9t m\u1ed1i quan h\u1ec7 \u0111\u01b0\u1ee3c th\u00eam ho\u1eb7c x\u00f3a, h\u00e3y c\u1eadp nh\u1eadt s\u01a1 \u0111\u1ed3 ngay l\u1eadp t\u1ee9c. C\u00e1c s\u01a1 \u0111\u1ed3 l\u1ed7i th\u1eddi d\u1eabn \u0111\u1ebfn hi\u1ec3u l\u1ea7m v\u00e0 l\u1ed7i trong t\u01b0\u01a1ng lai.<\/li>\n<\/ul>\n

            Xem x\u00e9t c\u00e1c h\u1ec7 th\u1ed1ng c\u0169<\/h3>\n

            C\u00e1c h\u1ec7 th\u1ed1ng c\u0169 th\u01b0\u1eddng c\u00f3 c\u00e1c m\u1ed1i quan h\u1ec7 kh\u00f4ng \u0111\u01b0\u1ee3c t\u00e0i li\u1ec7u h\u00f3a. Khi kh\u1eafc ph\u1ee5c s\u1ef1 c\u1ed1 trong c\u00e1c m\u00f4i tr\u01b0\u1eddng n\u00e0y, h\u00e3y c\u1ea9n tr\u1ecdng. Kh\u00f4ng n\u00ean gi\u1ea3 \u0111\u1ecbnh s\u01a1 \u0111\u1ed3 l\u00e0 \u0111\u00fang. Ph\u00e2n t\u00edch l\u1ea1i l\u01b0\u1ee3c \u0111\u1ed3 b\u1eb1ng c\u00e1ch ph\u00e2n t\u00edch c\u00e1c r\u00e0ng bu\u1ed9c kh\u00f3a ngo\u1ea1i trong c\u01a1 s\u1edf d\u1eef li\u1ec7u. T\u00ecm ki\u1ebfm c\u00e1c r\u00e0ng bu\u1ed9c kh\u00f4ng \u0111\u01b0\u1ee3c th\u1ef1c thi (v\u00f4 hi\u1ec7u h\u00f3a) nh\u01b0ng v\u1eabn t\u1ed3n t\u1ea1i trong d\u1eef li\u1ec7u m\u00f4 t\u1ea3. Nh\u1eefng r\u00e0ng bu\u1ed9c n\u00e0y th\u01b0\u1eddng l\u00e0 di t\u00edch c\u1ee7a c\u00e1c n\u1ed7 l\u1ef1c thi\u1ebft k\u1ebf tr\u01b0\u1edbc \u0111\u00f3.<\/p>\n

            \u0110\u00e0o t\u1ea1o v\u00e0 H\u1ee3p t\u00e1c<\/h3>\n

            M\u00f4 h\u00ecnh h\u00f3a d\u1eef li\u1ec7u l\u00e0 m\u1ed9t n\u1ed7 l\u1ef1c h\u1ee3p t\u00e1c. C\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n, DBA v\u00e0 chuy\u00ean vi\u00ean ph\u00e2n t\u00edch kinh doanh ph\u1ea3i th\u1ed1ng nh\u1ea5t v\u1ec1 c\u00e1c quy t\u1eafc. S\u1ef1 hi\u1ec3u l\u1ea7m th\u01b0\u1eddng d\u1eabn \u0111\u1ebfn c\u00e1c \u201cl\u1ed7i im l\u1eb7ng\u201d trong s\u01a1 \u0111\u1ed3 ERD. T\u1ed5 ch\u1ee9c c\u00e1c bu\u1ed5i xem x\u00e9t \u0111\u1ecbnh k\u1ef3, trong \u0111\u00f3 s\u01a1 \u0111\u1ed3 \u0111\u01b0\u1ee3c tr\u00ecnh b\u00e0y c\u00f9ng \u0111\u1ed9i ng\u0169. \u0110\u1eb7t c\u00e1c c\u00e2u h\u1ecfi c\u1ee5 th\u1ec3 v\u1ec1 c\u00e1c tr\u01b0\u1eddng h\u1ee3p bi\u00ean: \u201c\u0110i\u1ec1u g\u00ec x\u1ea3y ra n\u1ebfu tr\u01b0\u1eddng n\u00e0y b\u1ecb x\u00f3a?\u201d \u201c\u0110i\u1ec1u g\u00ec x\u1ea3y ra n\u1ebfu m\u1ed1i quan h\u1ec7 n\u00e0y b\u1ecb ph\u00e1 v\u1ee1?\u201d Vi\u1ec7c \u0111\u1eb7t c\u00e2u h\u1ecfi ch\u1ee7 \u0111\u1ed9ng n\u00e0y gi\u00fap ph\u00e1t hi\u1ec7n ra nh\u1eefng h\u1ed7n lo\u1ea1n ti\u1ec1m t\u00e0ng tr\u01b0\u1edbc khi ch\u00fang x\u1ea3y ra.<\/p>\n

            K\u1ebft lu\u1eadn v\u1ec1 t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u \ud83c\udfc1<\/h2>\n

            Duy tr\u00ec m\u1ed9t s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 l\u00e0nh m\u1ea1nh l\u00e0 \u0111i\u1ec1u c\u1ea7n thi\u1ebft cho b\u1ea5t k\u1ef3 \u1ee9ng d\u1ee5ng n\u00e0o ph\u1ee5 thu\u1ed9c v\u00e0o d\u1eef li\u1ec7u c\u00f3 c\u1ea5u tr\u00fac. C\u00e1c m\u1ed1i quan h\u1ec7 b\u1ecb h\u1ecfng t\u1ea1o ra m\u1ed9t n\u1ec1n t\u1ea3ng mong manh c\u00f3 th\u1ec3 s\u1ee5p \u0111\u1ed5 d\u01b0\u1edbi t\u1ea3i ho\u1eb7c trong qu\u00e1 tr\u00ecnh c\u1eadp nh\u1eadt. B\u1eb1ng c\u00e1ch hi\u1ec3u r\u00f5 t\u00ednh cardinality, x\u00e1c minh c\u00e1c r\u00e0ng bu\u1ed9c v\u00e0 tu\u00e2n theo quy tr\u00ecnh ch\u1ea9n \u0111o\u00e1n nghi\u00eam ng\u1eb7t, b\u1ea1n c\u00f3 th\u1ec3 \u0111\u1ea3m b\u1ea3o d\u1eef li\u1ec7u c\u1ee7a m\u00ecnh v\u1eabn ch\u00ednh x\u00e1c v\u00e0 d\u1ec5 truy c\u1eadp.<\/p>\n

            T\u1eadp trung v\u00e0o ph\u00f2ng ng\u1eeba th\u00f4ng qua t\u00e0i li\u1ec7u h\u00f3a v\u00e0 t\u1ef1 \u0111\u1ed9ng h\u00f3a. C\u00e1c cu\u1ed9c ki\u1ec3m tra \u0111\u1ecbnh k\u1ef3 s\u1ebd ph\u00e1t hi\u1ec7n s\u1ef1 l\u1ec7ch l\u1ea1c tr\u01b0\u1edbc khi n\u00f3 tr\u1edf th\u00e0nh kh\u1ee7ng ho\u1ea3ng. Xem s\u01a1 \u0111\u1ed3 ERD nh\u01b0 m\u1ed9t t\u00e0i li\u1ec7u s\u1ed1ng \u0111\u1ed9ng, lu\u00f4n thay \u0111\u1ed5i theo nhu c\u1ea7u kinh doanh c\u1ee7a b\u1ea1n. V\u1edbi nh\u1eefng th\u1ef1c h\u00e0nh n\u00e0y, c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n s\u1ebd v\u1eabn l\u00e0 m\u1ed9t t\u00e0i s\u1ea3n \u0111\u00e1ng tin c\u1eady thay v\u00ec ngu\u1ed3n r\u1ee7i ro v\u1eadn h\u00e0nh.<\/p>\n

            H\u00e3y nh\u1edb r\u1eb1ng t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u kh\u00f4ng ch\u1ec9 l\u00e0 ng\u0103n ng\u1eeba l\u1ed7i; \u0111\u00f3 l\u00e0 \u0111\u1ea3m b\u1ea3o s\u1ef1 tin t\u01b0\u1edfng v\u00e0o th\u00f4ng tin m\u00e0 h\u1ec7 th\u1ed1ng c\u1ee7a b\u1ea1n cung c\u1ea5p. M\u1ed9t m\u00f4 h\u00ecnh \u0111\u01b0\u1ee3c duy tr\u00ec t\u1ed1t s\u1ebd h\u1ed7 tr\u1ee3 ra quy\u1ebft \u0111\u1ecbnh t\u1ed1t h\u01a1n v\u00e0 ho\u1ea1t \u0111\u1ed9ng tr\u01a1n tru h\u01a1n. Gi\u1eef c\u00e1c m\u1ed1i quan h\u1ec7 r\u00f5 r\u00e0ng, c\u00e1c r\u00e0ng bu\u1ed9c \u0111\u01b0\u1ee3c th\u1ef1c thi v\u00e0 t\u00e0i li\u1ec7u lu\u00f4n \u0111\u01b0\u1ee3c c\u1eadp nh\u1eadt.<\/p>\n","protected":false},"excerpt":{"rendered":"

            S\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 (ERD) \u0111\u00f3ng vai tr\u00f2 nh\u01b0 b\u1ea3n v\u1ebd thi\u1ebft k\u1ebf cho ki\u1ebfn tr\u00fac c\u01a1 s\u1edf d\u1eef li\u1ec7u. Ch\u00fang x\u00e1c \u0111\u1ecbnh c\u00e1ch d\u1eef li\u1ec7u k\u1ebft n\u1ed1i,…<\/p>\n","protected":false},"author":1,"featured_media":1578,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_yoast_wpseo_title":"Kh\u1eafc ph\u1ee5c s\u1ef1 c\u1ed1 ERD: S\u1eeda c\u00e1c m\u1ed1i quan h\u1ec7 b\u1ecb h\u1ecfng \u2699\ufe0f","_yoast_wpseo_metadesc":"H\u1ecdc c\u00e1ch nh\u1eadn di\u1ec7n v\u00e0 kh\u1eafc ph\u1ee5c c\u00e1c l\u1ed7i m\u1ed1i quan h\u1ec7 ERD. \u0110\u1ea3m b\u1ea3o t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u v\u00e0 ng\u0103n ch\u1eb7n h\u1ed7n lo\u1ea1n c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u1edbi h\u01b0\u1edbng d\u1eabn kh\u1eafc ph\u1ee5c s\u1ef1 c\u1ed1 to\u00e0n di\u1ec7n n\u00e0y.","fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[88],"tags":[84,87],"class_list":["post-1577","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-erd","tag-academic","tag-erd"],"yoast_head":"\nKh\u1eafc ph\u1ee5c s\u1ef1 c\u1ed1 ERD: S\u1eeda c\u00e1c m\u1ed1i quan h\u1ec7 b\u1ecb h\u1ecfng \u2699\ufe0f<\/title>\n<meta name=\"description\" content=\"H\u1ecdc c\u00e1ch nh\u1eadn di\u1ec7n v\u00e0 kh\u1eafc ph\u1ee5c c\u00e1c l\u1ed7i m\u1ed1i quan h\u1ec7 ERD. \u0110\u1ea3m b\u1ea3o t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u v\u00e0 ng\u0103n ch\u1eb7n h\u1ed7n lo\u1ea1n c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u1edbi h\u01b0\u1edbng d\u1eabn kh\u1eafc ph\u1ee5c s\u1ef1 c\u1ed1 to\u00e0n di\u1ec7n n\u00e0y.\" \/>\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\/erd-troubleshooting-guide-fixing-broken-relationships\/\" \/>\n<meta property=\"og:locale\" content=\"vi_VN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Kh\u1eafc ph\u1ee5c s\u1ef1 c\u1ed1 ERD: S\u1eeda c\u00e1c m\u1ed1i quan h\u1ec7 b\u1ecb h\u1ecfng \u2699\ufe0f\" \/>\n<meta property=\"og:description\" content=\"H\u1ecdc c\u00e1ch nh\u1eadn di\u1ec7n v\u00e0 kh\u1eafc ph\u1ee5c c\u00e1c l\u1ed7i m\u1ed1i quan h\u1ec7 ERD. \u0110\u1ea3m b\u1ea3o t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u v\u00e0 ng\u0103n ch\u1eb7n h\u1ed7n lo\u1ea1n c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u1edbi h\u01b0\u1edbng d\u1eabn kh\u1eafc ph\u1ee5c s\u1ef1 c\u1ed1 to\u00e0n di\u1ec7n n\u00e0y.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.viz-read.com\/vi\/erd-troubleshooting-guide-fixing-broken-relationships\/\" \/>\n<meta property=\"og:site_name\" content=\"Viz Read Vietnamese - 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