{"id":1541,"date":"2026-03-27T07:19:03","date_gmt":"2026-03-27T07:19:03","guid":{"rendered":"https:\/\/www.viz-read.com\/vi\/erd-normalization-guide-when-to-stop-further\/"},"modified":"2026-03-27T07:19:03","modified_gmt":"2026-03-27T07:19:03","slug":"erd-normalization-guide-when-to-stop-further","status":"publish","type":"post","link":"https:\/\/www.viz-read.com\/vi\/erd-normalization-guide-when-to-stop-further\/","title":{"rendered":"S\u1ef1 Th\u1eadt V\u1ec1 Chu\u1ea9n H\u00f3a ERD: Khi N\u00e0o Th\u00ec D\u1eebng L\u1ea1i V\u00e0 Khi N\u00e0o Th\u00ec Ti\u1ebfn T\u1edbi H\u01a1n N\u1eefa"},"content":{"rendered":"

Thi\u1ebft k\u1ebf m\u1ed9t m\u00f4 h\u00ecnh d\u1eef li\u1ec7u m\u1ea1nh m\u1ebd l\u00e0 m\u1ed9t trong nh\u1eefng nhi\u1ec7m v\u1ee5 quan tr\u1ecdng nh\u1ea5t trong k\u1ef9 thu\u1eadt ph\u1ea7n m\u1ec1m. 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 c\u00e1ch th\u00f4ng tin \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef, truy xu\u1ea5t v\u00e0 duy tr\u00ec. \u1ede trung t\u00e2m c\u1ee7a b\u1ea3n v\u1ebd thi\u1ebft k\u1ebf n\u00e0y l\u00e0 chu\u1ea9n h\u00f3a. Nhi\u1ec1u chuy\u00ean gia ti\u1ebfp c\u1eadn chu\u1ea9n h\u00f3a nh\u01b0 m\u1ed9t danh s\u00e1ch ki\u1ec3m tra c\u1ee9ng nh\u1eafc c\u1ea7n ho\u00e0n th\u00e0nh tr\u01b0\u1edbc khi chuy\u1ec3n sang tri\u1ec3n khai. Tuy nhi\u00ean, th\u1ef1c t\u1ebf l\u1ea1i ph\u1ee9c t\u1ea1p h\u01a1n nhi\u1ec1u. C\u00f3 m\u1ed9t s\u1ef1 c\u00e2n b\u1eb1ng tinh t\u1ebf gi\u1eefa t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u v\u00e0 hi\u1ec7u su\u1ea5t truy v\u1ea5n, \u0111\u00f2i h\u1ecfi s\u1ef1 hi\u1ec3u bi\u1ebft s\u00e2u s\u1eafc.<\/p>\n

H\u01b0\u1edbng d\u1eabn n\u00e0y kh\u00e1m ph\u00e1 c\u00e1c th\u1ef1c t\u1ebf k\u1ef9 thu\u1eadt v\u1ec1 chu\u1ea9n h\u00f3a ERD. N\u00f3 v\u01b0\u1ee3t ra ngo\u00e0i c\u00e1c \u0111\u1ecbnh ngh\u0129a trong s\u00e1ch gi\u00e1o khoa \u0111\u1ec3 gi\u1ea3i quy\u1ebft c\u00e1c t\u00ecnh hu\u1ed1ng th\u1ef1c t\u1ebf m\u00e0 vi\u1ec7c tu\u00e2n th\u1ee7 nghi\u00eam ng\u1eb7t c\u00e1c quy t\u1eafc tr\u1edf th\u00e0nh m\u1ed9t r\u1ee7i ro. D\u00f9 b\u1ea1n \u0111ang x\u00e2y d\u1ef1ng h\u1ec7 th\u1ed1ng giao d\u1ecbch hay n\u1ec1n t\u1ea3ng ph\u00e2n t\u00edch, vi\u1ec7c bi\u1ebft khi n\u00e0o n\u00ean d\u1eebng chu\u1ea9n h\u00f3a v\u00e0 khi n\u00e0o n\u00ean \u0111\u01b0a ra s\u1ef1 tr\u00f9ng l\u1eb7p d\u1eef li\u1ec7u l\u00e0 \u0111i\u1ec1u thi\u1ebft y\u1ebfu \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o s\u1ef1 \u1ed5n \u0111\u1ecbnh l\u00e2u d\u00e0i.<\/p>\n

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\"Hand-drawn<\/figure>\n<\/div>\n

\ud83d\udd0d Hi\u1ec3u r\u00f5 c\u00e1c Nguy\u00ean t\u1eafc C\u1ed1t l\u00f5i c\u1ee7a Thi\u1ebft k\u1ebf Quan h\u1ec7<\/h2>\n

Chu\u1ea9n h\u00f3a kh\u00f4ng ch\u1ec9 \u0111\u01a1n thu\u1ea7n l\u00e0 s\u1eafp x\u1ebfp d\u1eef li\u1ec7u; n\u00f3 l\u00e0 vi\u1ec7c qu\u1ea3n l\u00fd c\u00e1c m\u1ed1i ph\u1ee5 thu\u1ed9c. Trong m\u00f4 h\u00ecnh quan h\u1ec7, m\u1ed7i c\u1ed9t ph\u1ea3i c\u00f3 m\u1ed1i quan h\u1ec7 r\u00f5 r\u00e0ng v\u1edbi kh\u00f3a ch\u00ednh c\u1ee7a b\u1ea3ng ch\u1ee9a n\u00f3. Khi m\u1ed1i quan h\u1ec7 n\u00e0y y\u1ebfu ho\u1eb7c gi\u00e1n ti\u1ebfp, c\u00e1c b\u1ea5t th\u01b0\u1eddng s\u1ebd x\u1ea3y ra. Nh\u1eefng b\u1ea5t th\u01b0\u1eddng n\u00e0y th\u1ec3 hi\u1ec7n d\u01b0\u1edbi d\u1ea1ng s\u1ef1 kh\u00f4ng nh\u1ea5t qu\u00e1n d\u1eef li\u1ec7u, l\u00e3ng ph\u00ed kh\u00f4ng gian l\u01b0u tr\u1eef v\u00e0 logic c\u1eadp nh\u1eadt ph\u1ee9c t\u1ea1p.<\/p>\n

C\u00e1c m\u1ee5c ti\u00eau ch\u00ednh c\u1ee7a chu\u1ea9n h\u00f3a bao g\u1ed3m:<\/p>\n

    \n
  • To\u00e0n v\u1eb9n D\u1eef li\u1ec7u:<\/strong>\u0110\u1ea3m b\u1ea3o d\u1eef li\u1ec7u lu\u00f4n ch\u00ednh x\u00e1c v\u00e0 nh\u1ea5t qu\u00e1n trong to\u00e0n h\u1ec7 th\u1ed1ng.<\/li>\n
  • Hi\u1ec7u qu\u1ea3 L\u01b0u tr\u1eef:<\/strong>Lo\u1ea1i b\u1ecf c\u00e1c b\u1ea3n sao tr\u00f9ng l\u1eb7p c\u1ee7a c\u00f9ng m\u1ed9t d\u1eef li\u1ec7u.<\/li>\n
  • Kh\u1ea3 n\u0103ng M\u1edf r\u1ed9ng:<\/strong>Thi\u1ebft k\u1ebf c\u00e1c l\u01b0\u1ee3c \u0111\u1ed3 c\u00f3 th\u1ec3 ch\u1ea5p nh\u1eadn s\u1ef1 ph\u00e1t tri\u1ec3n m\u00e0 kh\u00f4ng c\u1ea7n s\u1eeda \u0111\u1ed5i c\u1ea5u tr\u00fac.<\/li>\n
  • Kh\u1ea3 n\u0103ng B\u1ea3o tr\u00ec:<\/strong>Gi\u1ea3m thi\u1ec3u \u0111\u1ed9 ph\u1ee9c t\u1ea1p c\u1ea7n thi\u1ebft \u0111\u1ec3 c\u1eadp nh\u1eadt th\u00f4ng tin.<\/li>\n<\/ul>\n

    Tuy nhi\u00ean, \u0111\u1ea1t \u0111\u01b0\u1ee3c c\u00e1c m\u1ee5c ti\u00eau n\u00e0y th\u01b0\u1eddng \u0111i k\u00e8m v\u1edbi chi ph\u00ed. M\u1ed7i c\u1ea5p \u0111\u1ed9 chu\u1ea9n h\u00f3a th\u01b0\u1eddng l\u00e0m t\u0103ng s\u1ed1 l\u01b0\u1ee3ng b\u1ea3ng v\u00e0 \u0111\u1ed9 ph\u1ee9c t\u1ea1p c\u1ee7a c\u00e1c truy v\u1ea5n c\u1ea7n thi\u1ebft \u0111\u1ec3 truy xu\u1ea5t d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c n\u1ed1i k\u1ebft. Hi\u1ec3u r\u00f5 s\u1ef1 \u0111\u00e1nh \u0111\u1ed5i n\u00e0y l\u00e0 b\u01b0\u1edbc \u0111\u1ea7u ti\u00ean trong thi\u1ebft k\u1ebf l\u01b0\u1ee3c \u0111\u1ed3 hi\u1ec7u qu\u1ea3.<\/p>\n

    \u2699\ufe0f Ba tr\u1ee5 c\u1ed9t c\u1ee7a Chu\u1ea9n h\u00f3a Chu\u1ea9n (1NF, 2NF, 3NF)<\/h2>\n

    Tr\u01b0\u1edbc khi quy\u1ebft \u0111\u1ecbnh d\u1eebng l\u1ea1i hay ti\u1ebfp t\u1ee5c, ta ph\u1ea3i hi\u1ec3u r\u00f5 n\u1ec1n t\u1ea3ng c\u01a1 b\u1ea3n. C\u00e1c d\u1ea1ng chu\u1ea9n cung c\u1ea5p m\u1ed9t thang b\u1eadc c\u1ee7a s\u1ef1 tinh ch\u1ec9nh c\u1ea5u tr\u00fac.<\/p>\n

    D\u1ea1ng chu\u1ea9n th\u1ee9 nh\u1ea5t (1NF)<\/h3>\n

    N\u1ec1n t\u1ea3ng c\u1ee7a b\u1ea5t k\u1ef3 c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 n\u00e0o l\u00e0 1NF. M\u1ed9t b\u1ea3ng \u1edf 1NF n\u1ebfu n\u00f3 \u0111\u00e1p \u1ee9ng c\u00e1c ti\u00eau ch\u00ed sau:<\/p>\n

      \n
    • T\u1ea5t c\u1ea3 c\u00e1c gi\u00e1 tr\u1ecb c\u1ed9t \u0111\u1ec1u nguy\u00ean t\u1eed (kh\u00f4ng th\u1ec3 chia nh\u1ecf).<\/li>\n
    • M\u1ed7i c\u1ed9t ch\u1ee9a c\u00e1c gi\u00e1 tr\u1ecb thu\u1ed9c m\u1ed9t ki\u1ec3u duy nh\u1ea5t.<\/li>\n
    • Kh\u00f4ng c\u00f3 nh\u00f3m l\u1eb7p l\u1ea1i hay m\u1ea3ng trong m\u1ed9t h\u00e0ng.<\/li>\n<\/ul>\n

      V\u00ed d\u1ee5, vi\u1ec7c l\u01b0u tr\u1eef danh s\u00e1ch t\u00ean s\u1ea3n ph\u1ea9m trong m\u1ed9t c\u1ed9t duy nh\u1ea5t vi ph\u1ea1m 1NF. Thay v\u00e0o \u0111\u00f3, m\u1ed7i s\u1ea3n ph\u1ea9m n\u00ean chi\u1ebfm m\u1ed9t h\u00e0ng ri\u00eang bi\u1ec7t. M\u1eb7c d\u00f9 c\u00e1c h\u1ec7 th\u1ed1ng hi\u1ec7n \u0111\u1ea1i th\u01b0\u1eddng x\u1eed l\u00fd \u0111\u01b0\u1ee3c c\u00e1c ki\u1ec3u d\u1eef li\u1ec7u ph\u1ee9c t\u1ea1p, nh\u01b0ng vi\u1ec7c tu\u00e2n th\u1ee7 nghi\u00eam ng\u1eb7t t\u00ednh nguy\u00ean t\u1eed \u0111\u1ea3m b\u1ea3o c\u00e1c truy v\u1ea5n v\u1eabn c\u00f3 th\u1ec3 d\u1ef1 \u0111o\u00e1n \u0111\u01b0\u1ee3c v\u00e0 c\u00e1c chi\u1ebfn l\u01b0\u1ee3c l\u1eadp ch\u1ec9 m\u1ee5c ho\u1ea1t \u0111\u1ed9ng nh\u01b0 mong \u0111\u1ee3i.<\/p>\n

      D\u1ea1ng chu\u1ea9n th\u1ee9 hai (2NF)<\/h3>\n

      Khi m\u1ed9t b\u1ea3ng \u0111\u00e3 \u1edf 1NF, n\u00f3 ph\u1ea3i \u0111\u00e1p \u1ee9ng c\u00e1c y\u00eau c\u1ea7u c\u1ee7a 2NF. D\u1ea1ng n\u00e0y \u00e1p d\u1ee5ng ri\u00eang cho c\u00e1c b\u1ea3ng c\u00f3 kh\u00f3a ch\u00ednh h\u1ee3p th\u00e0nh (kh\u00f3a g\u1ed3m nhi\u1ec1u c\u1ed9t). M\u1ed9t b\u1ea3ng \u1edf 2NF n\u1ebfu:<\/p>\n

        \n
      • N\u00f3 \u0111\u00e3 \u1edf 1NF.<\/li>\n
      • T\u1ea5t c\u1ea3 c\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng ph\u1ea3i kh\u00f3a \u0111\u1ec1u ph\u1ee5 thu\u1ed9c ho\u00e0n to\u00e0n v\u00e0o to\u00e0n b\u1ed9 kh\u00f3a ch\u00ednh, ch\u1ee9 kh\u00f4ng ch\u1ec9 m\u1ed9t ph\u1ea7n c\u1ee7a n\u00f3.<\/li>\n<\/ul>\n

        H\u00e3y xem x\u00e9t m\u1ed9t b\u1ea3ng chi ti\u1ebft \u0111\u01a1n h\u00e0ng, n\u01a1i kh\u00f3a l\u00e0 s\u1ef1 k\u1ebft h\u1ee3p gi\u1eefa ID \u0111\u01a1n h\u00e0ng v\u00e0 ID s\u1ea3n ph\u1ea9m. N\u1ebfu b\u1ea1n l\u01b0u t\u00ean s\u1ea3n ph\u1ea9m trong b\u1ea3ng n\u00e0y, b\u1ea1n s\u1ebd c\u00f3 m\u1ed9t ph\u1ee5 thu\u1ed9c ri\u00eang ph\u1ea7n. T\u00ean s\u1ea3n ph\u1ea9m ch\u1ec9 ph\u1ee5 thu\u1ed9c v\u00e0o ID s\u1ea3n ph\u1ea9m, ch\u1ee9 kh\u00f4ng ph\u1ee5 thu\u1ed9c v\u00e0o ID \u0111\u01a1n h\u00e0ng. \u0110\u1ec3 kh\u1eafc ph\u1ee5c, b\u1ea1n di chuy\u1ec3n t\u00ean s\u1ea3n ph\u1ea9m sang m\u1ed9t b\u1ea3ng Products ri\u00eang bi\u1ec7t. \u0110i\u1ec1u n\u00e0y gi\u1ea3m thi\u1ec3u c\u00e1c b\u1ea5t th\u01b0\u1eddng khi c\u1eadp nh\u1eadt; n\u1ebfu t\u00ean s\u1ea3n ph\u1ea9m thay \u0111\u1ed5i, b\u1ea1n ch\u1ec9 c\u1ea7n c\u1eadp nh\u1eadt \u1edf m\u1ed9t n\u01a1i, ch\u1ee9 kh\u00f4ng ph\u1ea3i tr\u00ean h\u00e0ng ng\u00e0n b\u1ea3n ghi \u0111\u01a1n h\u00e0ng.<\/p>\n

        D\u1ea1ng chu\u1ea9n th\u1ee9 ba (3NF)<\/h3>\n

        3NF th\u01b0\u1eddng \u0111\u01b0\u1ee3c coi l\u00e0 \u0111i\u1ec3m t\u1ed1i \u01b0u cho ph\u1ea7n l\u1edbn c\u00e1c h\u1ec7 th\u1ed1ng v\u1eadn h\u00e0nh. M\u1ed9t b\u1ea3ng \u1edf 3NF n\u1ebfu:<\/p>\n

          \n
        • N\u00f3 \u1edf d\u1ea1ng chu\u1ea9n h\u00f3a th\u1ee9 hai (2NF).<\/li>\n
        • Kh\u00f4ng c\u00f3 ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u. C\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng kh\u00f3a ph\u1ea3i ph\u1ee5 thu\u1ed9c duy nh\u1ea5t v\u00e0o kh\u00f3a ch\u00ednh.<\/li>\n<\/ul>\n

          M\u1ed9t ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u x\u1ea3y ra khi C\u1ed9t A x\u00e1c \u0111\u1ecbnh C\u1ed9t B, v\u00e0 C\u1ed9t B x\u00e1c \u0111\u1ecbnh C\u1ed9t C. Trong m\u1ed9t c\u01a1 s\u1edf d\u1eef li\u1ec7u, n\u1ebfu M\u00e3 Kh\u00e1ch h\u00e0ng x\u00e1c \u0111\u1ecbnh Th\u00e0nh ph\u1ed1, v\u00e0 Th\u00e0nh ph\u1ed1 x\u00e1c \u0111\u1ecbnh V\u00f9ng, vi\u1ec7c l\u01b0u tr\u1eef V\u00f9ng trong b\u1ea3ng Kh\u00e1ch h\u00e0ng s\u1ebd t\u1ea1o ra m\u1ed9t ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u. N\u1ebfu V\u00f9ng thay \u0111\u1ed5i \u0111\u1ed1i v\u1edbi th\u00e0nh ph\u1ed1 \u0111\u00f3, b\u1ea1n ph\u1ea3i c\u1eadp nh\u1eadt m\u1ecdi b\u1ea3n ghi kh\u00e1ch h\u00e0ng trong th\u00e0nh ph\u1ed1 \u0111\u00f3. Chu\u1ea9n h\u00f3a \u0111i\u1ec1u n\u00e0y s\u1ebd di chuy\u1ec3n d\u1eef li\u1ec7u V\u00f9ng sang m\u1ed9t v\u1ecb tr\u00ed ri\u00eang bi\u1ec7t, \u0111\u1ea3m b\u1ea3o r\u1eb1ng vi\u1ec7c c\u1eadp nh\u1eadt ch\u1ec9 x\u1ea3y ra m\u1ed9t l\u1ea7n.<\/p>\n

          \ud83d\udcc9 Chi ph\u00ed hi\u1ec7u su\u1ea5t c\u1ee7a vi\u1ec7c chu\u1ea9n h\u00f3a nghi\u00eam ng\u1eb7t<\/h2>\n

          M\u1eb7c d\u00f9 3NF gi\u1ea3m thi\u1ec3u s\u1ef1 tr\u00f9ng l\u1eb7p, nh\u01b0ng l\u1ea1i l\u00e0m t\u0103ng s\u1ed1 l\u01b0\u1ee3ng b\u1ea3ng. Trong m\u1ed9t l\u01b0\u1ee3c \u0111\u1ed3 \u0111\u00e3 chu\u1ea9n h\u00f3a, vi\u1ec7c truy xu\u1ea5t m\u1ed9t b\u1ea3n ghi logic duy nh\u1ea5t th\u01b0\u1eddng \u0111\u00f2i h\u1ecfi ph\u1ea3i n\u1ed1i nhi\u1ec1u b\u1ea3ng. Qu\u00e1 tr\u00ecnh n\u00e0y c\u00f3 chi ph\u00ed t\u00ednh to\u00e1n.<\/p>\n

            \n
          • Chi ph\u00ed n\u1ed1i (Join Overhead):<\/strong>M\u1ed7i thao t\u00e1c n\u1ed1i y\u00eau c\u1ea7u b\u1ed9 \u0111\u1ed9ng c\u01a1 c\u01a1 s\u1edf d\u1eef li\u1ec7u ph\u1ea3i gh\u00e9p c\u00e1c h\u00e0ng t\u1eeb c\u00e1c b\u1ea3ng kh\u00e1c nhau. Khi c\u00e1c b\u1ea3ng l\u1edbn l\u00ean, qu\u00e1 tr\u00ecnh gh\u00e9p n\u00e0y ti\u00eau t\u1ed1n CPU v\u00e0 b\u1ed9 nh\u1edb.<\/li>\n
          • Thao t\u00e1c I\/O:<\/strong>D\u1eef li\u1ec7u ph\u00e2n b\u1ed1 tr\u00ean nhi\u1ec1u b\u1ea3ng \u0111\u00f2i h\u1ecfi nhi\u1ec1u thao t\u00e1c \u0111\u1ecdc \u0111\u0129a h\u01a1n. N\u1ebfu d\u1eef li\u1ec7u kh\u00f4ng \u0111\u01b0\u1ee3c l\u01b0u t\u1ea1m hi\u1ec7u qu\u1ea3, \u0111\u1ed9 tr\u1ec5 \u0111\u1ecdc s\u1ebd t\u0103ng l\u00ean.<\/li>\n
          • \u0110\u1ed9 ph\u1ee9c t\u1ea1p:<\/strong>C\u00e1c truy v\u1ea5n ph\u1ee9c t\u1ea1p v\u1edbi nhi\u1ec1u thao t\u00e1c n\u1ed1i kh\u00f3 t\u1ed1i \u01b0u h\u00f3a v\u00e0 b\u1ea3o tr\u00ec h\u01a1n. Ch\u00fang c\u0169ng d\u1ec5 b\u1ecb l\u1ed7i h\u01a1n n\u1ebfu l\u01b0\u1ee3c \u0111\u1ed3 thay \u0111\u1ed5i.<\/li>\n<\/ul>\n

            \u0110\u1ed1i v\u1edbi c\u00e1c h\u1ec7 th\u1ed1ng c\u00f3 t\u1ea3i ghi n\u1eb7ng, chu\u1ea9n h\u00f3a th\u01b0\u1eddng l\u00e0 l\u1ef1a ch\u1ecdn \u0111\u00fang \u0111\u1eafn. N\u00f3 ng\u0103n ng\u1eeba s\u1ef1 tr\u00f9ng l\u1eb7p d\u1eef li\u1ec7u v\u00e0 \u0111\u1ea3m b\u1ea3o r\u1eb1ng m\u1ed9t c\u1eadp nh\u1eadt \u0111\u1ed1i v\u1edbi m\u1ed9t s\u1ef1 ki\u1ec7n duy nh\u1ea5t \u0111\u01b0\u1ee3c lan truy\u1ec1n \u0111\u00fang c\u00e1ch. Tuy nhi\u00ean, \u0111\u1ed1i v\u1edbi c\u00e1c h\u1ec7 th\u1ed1ng c\u00f3 t\u1ea3i \u0111\u1ecdc n\u1eb7ng, chi ph\u00ed c\u1ee7a c\u00e1c thao t\u00e1c n\u1ed1i c\u00f3 th\u1ec3 tr\u1edf th\u00e0nh \u0111i\u1ec3m ngh\u1ebdn.<\/p>\n

            \ud83d\ude80 Chu\u1ea9n h\u00f3a chi\u1ebfn l\u01b0\u1ee3c: Khi n\u00e0o n\u00ean ph\u00e1 v\u1ee1 quy t\u1eafc<\/h2>\n

            Vi\u1ec7c kh\u00f4ng chu\u1ea9n h\u00f3a l\u00e0 vi\u1ec7c ch\u1ee7 \u00fd \u0111\u01b0a v\u00e0o s\u1ef1 tr\u00f9ng l\u1eb7p nh\u1eb1m t\u1ed1i \u01b0u hi\u1ec7u su\u1ea5t. \u0110\u00f3 kh\u00f4ng ph\u1ea3i l\u00e0 sai l\u1ea7m; \u0111\u00f3 l\u00e0 m\u1ed9t quy\u1ebft \u0111\u1ecbnh ki\u1ebfn tr\u00fac c\u00f3 ch\u1ee7 \u00fd \u0111\u01b0\u1ee3c \u0111\u01b0a ra khi chi ph\u00ed chu\u1ea9n h\u00f3a v\u01b0\u1ee3t qu\u00e1 l\u1ee3i \u00edch c\u1ee7a n\u00f3.<\/p>\n

            C\u00e1c \u0111i\u1ec1u ki\u1ec7n k\u00edch ho\u1ea1t vi\u1ec7c kh\u00f4ng chu\u1ea9n h\u00f3a<\/h3>\n

            B\u1ea1n n\u00ean c\u00e2n nh\u1eafc n\u1edbi l\u1ecfng c\u00e1c quy t\u1eafc chu\u1ea9n h\u00f3a khi:<\/p>\n

              \n
            • C\u00e1c thao t\u00e1c \u0111\u1ecdc chi\u1ebfm \u01b0u th\u1ebf:<\/strong>N\u1ebfu \u1ee9ng d\u1ee5ng c\u1ee7a b\u1ea1n c\u00f3 t\u1ea3i \u0111\u1ecdc n\u1eb7ng (v\u00ed d\u1ee5: b\u1ea3ng \u0111i\u1ec1u khi\u1ec3n b\u00e1o c\u00e1o), gi\u1ea3m s\u1ed1 thao t\u00e1c n\u1ed1i c\u00f3 th\u1ec3 l\u00e0m gi\u1ea3m \u0111\u00e1ng k\u1ec3 \u0111\u1ed9 tr\u1ec5.<\/li>\n
            • \u0110\u1ed9 ph\u1ee9c t\u1ea1p truy v\u1ea5n cao:<\/strong>N\u1ebfu ng\u01b0\u1eddi d\u00f9ng c\u1ea7n d\u1eef li\u1ec7u t\u1eeb 10 b\u1ea3ng tr\u1edf l\u00ean \u0111\u1ec3 xem m\u1ed9t trang duy nh\u1ea5t, truy v\u1ea5n s\u1ebd tr\u1edf n\u00ean ch\u1eadm v\u00e0 kh\u00f3 g\u1ee1 l\u1ed7i.<\/li>\n
            • T\u1ea7n su\u1ea5t ghi th\u1ea5p:<\/strong>N\u1ebfu d\u1eef li\u1ec7u hi\u1ebfm khi \u0111\u01b0\u1ee3c c\u1eadp nh\u1eadt, r\u1ee7i ro b\u1ea5t nh\u1ea5t do s\u1ef1 tr\u00f9ng l\u1eb7p s\u1ebd \u0111\u01b0\u1ee3c gi\u1ea3m thi\u1ec3u.<\/li>\n
            • T\u1ed3n t\u1ea1i gi\u1edbi h\u1ea1n v\u1ec1 ph\u1ea7n c\u1ee9ng:<\/strong>Trong c\u00e1c m\u00f4i tr\u01b0\u1eddng m\u00e0 I\/O \u0111\u0129a t\u1ed1n k\u00e9m ho\u1eb7c b\u1ecb gi\u1edbi h\u1ea1n, vi\u1ec7c l\u01b0u t\u1ea1m d\u1eef li\u1ec7u tr\u00f9ng l\u1eb7p c\u00f3 th\u1ec3 gi\u1ea3m s\u1ed1 l\u1ea7n \u0111\u1ecdc v\u1eadt l\u00fd.<\/li>\n<\/ul>\n

              C\u00e1c chi\u1ebfn l\u01b0\u1ee3c kh\u00f4ng chu\u1ea9n h\u00f3a ph\u1ed5 bi\u1ebfn<\/h3>\n
                \n
              • M\u1edf r\u1ed9ng c\u1ed9t:<\/strong>L\u01b0u tr\u1eef m\u1ed9t gi\u00e1 tr\u1ecb \u0111\u01b0\u1ee3c suy ra tr\u1ef1c ti\u1ebfp trong m\u1ed9t b\u1ea3ng. V\u00ed d\u1ee5: th\u00eam c\u1ed9t \u201cT\u1ed5ng gi\u00e1\u201d v\u00e0o b\u1ea3ng \u0110\u01a1n h\u00e0ng, \u0111\u01b0\u1ee3c t\u00ednh t\u1eeb c\u00e1c m\u1ee5c chi ti\u1ebft, \u0111\u1ec3 b\u1ea1n kh\u00f4ng c\u1ea7n ph\u1ea3i c\u1ed9ng d\u1ed3n ch\u00fang m\u1ed7i l\u1ea7n \u0111\u1ecdc.<\/li>\n
              • Kh\u00f3a ngo\u1ea1i tr\u00f9ng l\u1eb7p:<\/strong>Th\u00eam M\u00e3 cha v\u00e0o b\u1ea3ng con \u0111\u1ec3 tr\u00e1nh thao t\u00e1c n\u1ed1i khi truy xu\u1ea5t c\u1ea5u tr\u00fac ph\u00e2n c\u1ea5p.<\/li>\n
              • B\u1ea3ng t\u00f3m t\u1eaft:<\/strong> Ti\u1ec1n t\u00ednh to\u00e1n c\u00e1c t\u1ed5ng h\u1ee3p (\u0111\u1ebfm, t\u1ed5ng) trong m\u1ed9t b\u1ea3ng ri\u00eang bi\u1ec7t \u0111\u01b0\u1ee3c c\u1eadp nh\u1eadt \u0111\u1ecbnh k\u1ef3 ho\u1eb7c th\u00f4ng qua c\u00e1c tr\u00ecnh k\u00edch ho\u1ea1t.<\/li>\n
              • C\u00e1c View \u0111\u00e3 \u0111\u01b0\u1ee3c v\u1eadt ch\u1ea5t h\u00f3a:<\/strong>L\u01b0u k\u1ebft qu\u1ea3 c\u1ee7a m\u1ed9t truy v\u1ea5n ph\u1ee9c t\u1ea1p d\u01b0\u1edbi d\u1ea1ng b\u1ea3ng v\u1eadt l\u00fd \u0111\u01b0\u1ee3c l\u00e0m m\u1edbi theo l\u1ecbch tr\u00ecnh.<\/li>\n<\/ul>\n

                \ud83d\udcca So s\u00e1nh: Chu\u1ea9n h\u00f3a vs. Phi chu\u1ea9n h\u00f3a<\/h2>\n

                \u0110\u1ec3 h\u00ecnh dung r\u00f5 c\u00e1c \u0111i\u1ec3m \u0111\u00e1nh \u0111\u1ed5i, h\u00e3y xem b\u1ea3ng so s\u00e1nh sau.<\/p>\n\n\n\n\n\n\n\n\n\n\n
                Kh\u00eda c\u1ea1nh<\/th>\nChu\u1ea9n h\u00f3a cao (3NF+)<\/th>\nThi\u1ebft k\u1ebf phi chu\u1ea9n h\u00f3a<\/th>\n<\/tr>\n<\/thead>\n
                \u0110\u1ed9 to\u00e0n v\u1eb9n d\u1eef li\u1ec7u<\/td>\nCao \u2013 Ngu\u1ed3n duy nh\u1ea5t c\u1ee7a s\u1ef1 th\u1eadt<\/td>\nTh\u1ea5p \u2013 C\u1ea7n logic \u0111\u1ed3ng b\u1ed9 h\u00f3a<\/td>\n<\/tr>\n
                S\u1eed d\u1ee5ng b\u1ed9 nh\u1edb<\/td>\nHi\u1ec7u qu\u1ea3 \u2013 Kh\u00f4ng c\u00f3 b\u1ea3n sao<\/td>\nKh\u00f4ng hi\u1ec7u qu\u1ea3 \u2013 D\u1eef li\u1ec7u tr\u00f9ng l\u1eb7p<\/td>\n<\/tr>\n
                Hi\u1ec7u su\u1ea5t ghi<\/td>\nNhanh \u2013 C\u1eadp nh\u1eadt m\u1ed9t h\u00e0ng duy nh\u1ea5t<\/td>\nCh\u1eadm h\u01a1n \u2013 C\u1eadp nh\u1eadt nhi\u1ec1u h\u00e0ng<\/td>\n<\/tr>\n
                Hi\u1ec7u su\u1ea5t \u0111\u1ecdc<\/td>\nCh\u1eadm h\u01a1n \u2013 C\u1ea7n c\u00e1c ph\u00e9p n\u1ed1i<\/td>\nNhanh \u2013 Truy c\u1eadp tr\u1ef1c ti\u1ebfp<\/td>\n<\/tr>\n
                \u0110\u1ed9 ph\u1ee9c t\u1ea1p truy v\u1ea5n<\/td>\nCao \u2013 C\u1ea7n nhi\u1ec1u ph\u00e9p n\u1ed1i<\/td>\nTh\u1ea5p \u2013 Truy v\u1ea5n \u0111\u01a1n gi\u1ea3n<\/td>\n<\/tr>\n
                N\u1ed7 l\u1ef1c b\u1ea3o tr\u00ec<\/td>\nTh\u1ea5p \u2013 C\u1eadp nh\u1eadt m\u1ed9t l\u1ea7n<\/td>\nCao \u2013 \u0110\u1ed3ng b\u1ed9 \u1edf nhi\u1ec1u n\u01a1i<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

                B\u1ea3ng n\u00e0y nh\u1ea5n m\u1ea1nh r\u1eb1ng kh\u00f4ng c\u00f3 ph\u01b0\u01a1ng ph\u00e1p t\u1ed1t nh\u1ea5t ph\u1ed5 qu\u00e1t. S\u1ef1 l\u1ef1a ch\u1ecdn ho\u00e0n to\u00e0n ph\u1ee5 thu\u1ed9c v\u00e0o kh\u1ed1i l\u01b0\u1ee3ng c\u00f4ng vi\u1ec7c c\u1ee5 th\u1ec3 c\u1ee7a \u1ee9ng d\u1ee5ng.<\/p>\n

                \ud83d\udee0\ufe0f Khung quy\u1ebft \u0111\u1ecbnh cho thi\u1ebft k\u1ebf l\u01b0\u1ee3c \u0111\u1ed3<\/h2>\n

                \u0110\u1ec3 x\u00e1c \u0111\u1ecbnh m\u1ee9c \u0111\u1ed9 chu\u1ea9n h\u00f3a ph\u00f9 h\u1ee3p cho d\u1ef1 \u00e1n c\u1ee5 th\u1ec3 c\u1ee7a b\u1ea1n, h\u00e3y s\u1eed d\u1ee5ng khung quy\u1ebft \u0111\u1ecbnh n\u00e0y. \u0110\u00e1nh gi\u00e1 t\u1eebng \u0111i\u1ec3m d\u1ef1a tr\u00ean y\u00eau c\u1ea7u d\u1ef1 \u00e1n c\u1ee7a b\u1ea1n.<\/p>\n

                1. Ph\u00e2n t\u00edch m\u1eabu kh\u1ed1i l\u01b0\u1ee3ng c\u00f4ng vi\u1ec7c<\/h3>\n

                X\u00e1c \u0111\u1ecbnh t\u1ef7 l\u1ec7 truy v\u1ea5n \u0111\u1ecdc so v\u1edbi ghi. N\u1ebfu h\u1ec7 th\u1ed1ng c\u1ee7a b\u1ea1n l\u00e0 OLTP (x\u1eed l\u00fd giao d\u1ecbch tr\u1ef1c tuy\u1ebfn), h\u00e3y \u01b0u ti\u00ean t\u00ednh to\u00e0n v\u1eb9n v\u00e0 d\u1ea1ng chu\u1ea9n h\u00f3a 3NF. N\u1ebfu l\u00e0 OLAP (x\u1eed l\u00fd ph\u00e2n t\u00edch tr\u1ef1c tuy\u1ebfn), h\u00e3y \u01b0u ti\u00ean t\u1ed1c \u0111\u1ed9 \u0111\u1ecdc v\u00e0 c\u00e2n nh\u1eafc vi\u1ec7c lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a.<\/p>\n

                2. \u0110\u00e1nh gi\u00e1 y\u00eau c\u1ea7u v\u1ec1 \u0111\u1ed9 m\u1edbi c\u1ee7a d\u1eef li\u1ec7u<\/h3>\n

                D\u1eef li\u1ec7u c\u00f3 c\u1ea7n c\u1eadp nh\u1eadt theo th\u1eddi gian th\u1ef1c kh\u00f4ng? N\u1ebfu b\u1ea1n lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a, s\u1ebd xu\u1ea5t hi\u1ec7n \u0111\u1ed9 tr\u1ec5 gi\u1eefa vi\u1ec7c c\u1eadp nh\u1eadt ngu\u1ed3n d\u1eef li\u1ec7u v\u00e0 thay \u0111\u1ed5i ph\u1ea3n \u00e1nh trong d\u1eef li\u1ec7u d\u01b0 th\u1eeba. N\u1ebfu ng\u01b0\u1eddi d\u00f9ng c\u1ea7n s\u1ef1 nh\u1ea5t qu\u00e1n t\u1ee9c th\u00ec, vi\u1ec7c chu\u1ea9n h\u00f3a nghi\u00eam ng\u1eb7t s\u1ebd an to\u00e0n h\u01a1n.<\/p>\n

                3. \u0110\u00e1nh gi\u00e1 t\u1ea7n su\u1ea5t c\u1eadp nh\u1eadt<\/h3>\n

                H\u00e3y xem x\u00e9t c\u00e1c kh\u00f3a ch\u00ednh. N\u1ebfu b\u1ea3ng tra c\u1ee9u (nh\u01b0 danh s\u00e1ch c\u00e1c qu\u1ed1c gia) thay \u0111\u1ed5i hi\u1ebfm khi, vi\u1ec7c lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a d\u1eef li\u1ec7u c\u1ee7a n\u00f3 v\u00e0o c\u00e1c b\u1ea3ng giao d\u1ecbch l\u00e0 an to\u00e0n. N\u1ebfu b\u1ea3ng tra c\u1ee9u thay \u0111\u1ed5i th\u01b0\u1eddng xuy\u00ean, h\u00e3y gi\u1eef n\u00f3 ri\u00eang bi\u1ec7t \u0111\u1ec3 gi\u1ea3m thi\u1ec3u l\u1ed7i \u0111\u1ed3ng b\u1ed9 h\u00f3a.<\/p>\n

                4. Xem x\u00e9t ph\u1ea7n c\u1ee9ng v\u00e0 b\u1ed9 nh\u1edb \u0111\u1ec7m<\/h3>\n

                C\u00e1c c\u01a1 s\u1edf d\u1eef li\u1ec7u hi\u1ec7n \u0111\u1ea1i th\u01b0\u1eddng l\u01b0u tr\u1eef d\u1eef li\u1ec7u trong b\u1ed9 nh\u1edb \u0111\u1ec7m. N\u1ebfu t\u1eadp d\u1eef li\u1ec7u l\u00e0m vi\u1ec7c c\u1ee7a b\u1ea1n v\u1eeba v\u1eb7n trong RAM, chi ph\u00ed c\u1ee7a c\u00e1c thao t\u00e1c n\u1ed1i (join) s\u1ebd gi\u1ea3m. Trong tr\u01b0\u1eddng h\u1ee3p n\u00e0y, b\u1ea1n c\u00f3 th\u1ec3 ch\u1ea5p nh\u1eadn m\u1ed9t l\u01b0\u1ee3c \u0111\u1ed3 chu\u1ea9n h\u00f3a h\u01a1n m\u1ed9t ch\u00fat m\u00e0 kh\u00f4ng l\u00e0m gi\u1ea3m hi\u1ec7u su\u1ea5t.<\/p>\n

                \ud83e\udde0 Chu\u1ea9n h\u00f3a n\u00e2ng cao: BCNF v\u00e0 4NF<\/h2>\n

                V\u01b0\u1ee3t qu\u00e1 3NF, c\u00f3 nh\u1eefng d\u1ea1ng chu\u1ea9n h\u00f3a cao h\u01a1n nh\u01b0 D\u1ea1ng chu\u1ea9n h\u00f3a Boyce-Codd (BCNF) v\u00e0 D\u1ea1ng chu\u1ea9n h\u00f3a th\u1ee9 t\u01b0 (4NF). Nh\u1eefng d\u1ea1ng n\u00e0y gi\u1ea3i quy\u1ebft c\u00e1c tr\u01b0\u1eddng h\u1ee3p \u0111\u1eb7c bi\u1ec7t.<\/p>\n

                D\u1ea1ng chu\u1ea9n h\u00f3a Boyce-Codd (BCNF)<\/h3>\n

                BCNF l\u00e0 phi\u00ean b\u1ea3n nghi\u00eam ng\u1eb7t h\u01a1n c\u1ee7a 3NF. N\u00f3 x\u1eed l\u00fd c\u00e1c tr\u01b0\u1eddng h\u1ee3p m\u00e0 m\u1ed9t thu\u1ed9c t\u00ednh kh\u00f4ng ch\u00ednh x\u00e1c \u0111\u1ecbnh m\u1ed9t thu\u1ed9c t\u00ednh kh\u00f4ng ch\u00ednh kh\u00e1c, ngay c\u1ea3 khi kh\u00f3a ch\u00ednh l\u00e0 h\u1ee3p th\u00e0nh. M\u1eb7c d\u00f9 l\u00fd thuy\u1ebft ho\u00e0n h\u1ea3o, BCNF \u0111\u00f4i khi d\u1eabn \u0111\u1ebfn m\u1ea5t t\u00ednh b\u1ea3o to\u00e0n ph\u1ee5 thu\u1ed9c. Trong th\u1ef1c t\u1ebf, 3NF th\u01b0\u1eddng l\u00e0 \u0111\u1ee7, v\u00e0 bu\u1ed9c \u00e1p d\u1ee5ng BCNF \u0111\u00f4i khi l\u00e0m ph\u1ee9c t\u1ea1p l\u01b0\u1ee3c \u0111\u1ed3 m\u00e0 kh\u00f4ng mang l\u1ea1i gi\u00e1 tr\u1ecb r\u00f5 r\u1ec7t.<\/p>\n

                D\u1ea1ng chu\u1ea9n h\u00f3a th\u1ee9 t\u01b0 (4NF)<\/h3>\n

                4NF x\u1eed l\u00fd c\u00e1c ph\u1ee5 thu\u1ed9c \u0111a gi\u00e1 tr\u1ecb. \u0110i\u1ec1u n\u00e0y x\u1ea3y ra khi m\u1ed9t h\u00e0ng duy nh\u1ea5t ch\u1ee9a nhi\u1ec1u danh s\u00e1ch gi\u00e1 tr\u1ecb \u0111\u1ed9c l\u1eadp. V\u00ed d\u1ee5, m\u1ed9t b\u1ea3ng sinh vi\u00ean l\u01b0u tr\u1eef nhi\u1ec1u s\u1edf th\u00edch v\u00e0 nhi\u1ec1u l\u1edbp h\u1ecdc trong c\u00f9ng m\u1ed9t h\u00e0ng. \u0110i\u1ec1u n\u00e0y hi\u1ebfm g\u1eb7p trong c\u00e1c \u1ee9ng d\u1ee5ng kinh doanh ti\u00eau chu\u1ea9n nh\u01b0ng ph\u1ed5 bi\u1ebfn trong c\u00e1c t\u00ecnh hu\u1ed1ng m\u00f4 h\u00ecnh h\u00f3a d\u1eef li\u1ec7u chuy\u00ean bi\u1ec7t.<\/p>\n

                \ud83d\udeab Nh\u1eefng sai l\u1ea7m ph\u1ed5 bi\u1ebfn c\u1ea7n tr\u00e1nh<\/h2>\n

                Ngay c\u1ea3 khi hi\u1ec3u r\u00f5 v\u1ec1 chu\u1ea9n h\u00f3a, vi\u1ec7c m\u1eafc sai l\u1ea7m v\u1eabn r\u1ea5t d\u1ec5 x\u1ea3y ra. H\u00e3y tr\u00e1nh nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn sau:<\/p>\n

                  \n
                • Chu\u1ea9n h\u00f3a qu\u00e1 m\u1ee9c:<\/strong>T\u1ea1o h\u00e0ng tr\u0103m b\u1ea3ng nh\u1ecf cho c\u00e1c m\u1ed1i quan h\u1ec7 \u0111\u01a1n gi\u1ea3n. \u0110i\u1ec1u n\u00e0y khi\u1ebfn logic \u1ee9ng d\u1ee5ng tr\u1edf n\u00ean kh\u00f3 theo d\u00f5i v\u00e0 l\u00e0m ch\u1eadm qu\u00e1 tr\u00ecnh ph\u00e1t tri\u1ec3n.<\/li>\n
                • B\u1ecf qua vi\u1ec7c s\u1eed d\u1ee5ng ch\u1ec9 m\u1ee5c:<\/strong>M\u1ed9t l\u01b0\u1ee3c \u0111\u1ed3 chu\u1ea9n h\u00f3a y\u00eau c\u1ea7u c\u00e1c thao t\u00e1c n\u1ed1i. N\u1ebfu c\u00e1c c\u1ed9t n\u1ed1i kh\u00f4ng \u0111\u01b0\u1ee3c ch\u1ec9 m\u1ee5c, hi\u1ec7u su\u1ea5t s\u1ebd suy gi\u1ea3m b\u1ea5t k\u1ec3 thi\u1ebft k\u1ebf l\u01b0\u1ee3c \u0111\u1ed3 nh\u01b0 th\u1ebf n\u00e0o.<\/li>\n
                • Lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a m\u00e0 kh\u00f4ng gi\u00e1m s\u00e1t:<\/strong>Vi\u1ec7c th\u00eam t\u00ednh d\u01b0 th\u1eeba m\u00e0 kh\u00f4ng c\u00f3 k\u1ebf ho\u1ea1ch \u0111\u1ed3ng b\u1ed9 h\u00f3a s\u1ebd d\u1eabn \u0111\u1ebfn l\u1ed7i d\u1eef li\u1ec7u theo th\u1eddi gian.<\/li>\n
                • G\u00e1n c\u1ee9ng logic:<\/strong>Kh\u00f4ng t\u00ednh to\u00e1n c\u00e1c gi\u00e1 tr\u1ecb \u0111\u01b0\u1ee3c suy ra \u1edf l\u1edbp \u1ee9ng d\u1ee5ng n\u1ebfu ch\u00fang n\u00ean n\u1eb1m trong c\u01a1 s\u1edf d\u1eef li\u1ec7u. Gi\u1eef c\u00e1c quy t\u1eafc kinh doanh g\u1ea7n v\u1edbi d\u1eef li\u1ec7u.<\/li>\n<\/ul>\n

                  \u2705 Danh s\u00e1ch ki\u1ec3m tra x\u00e1c minh l\u01b0\u1ee3c \u0111\u1ed3<\/h2>\n

                  Tr\u01b0\u1edbc khi tri\u1ec3n khai m\u1ed9t l\u01b0\u1ee3c \u0111\u1ed3 m\u1edbi, h\u00e3y th\u1ef1c hi\u1ec7n danh s\u00e1ch ki\u1ec3m tra x\u00e1c minh n\u00e0y.<\/p>\n

                    \n
                  • T\u00ednh nguy\u00ean t\u1eed:<\/strong>T\u1ea5t c\u1ea3 c\u00e1c tr\u01b0\u1eddng c\u00f3 t\u00ednh nguy\u00ean t\u1eed kh\u00f4ng?<\/li>\n
                  • Kh\u00f3a ch\u00ednh:<\/strong>M\u1ed7i b\u1ea3ng c\u00f3 kh\u00f3a ch\u00ednh duy nh\u1ea5t kh\u00f4ng?<\/li>\n
                  • Kh\u00f3a ngo\u1ea1i:<\/strong>C\u00e1c m\u1ed1i quan h\u1ec7 c\u00f3 \u0111\u01b0\u1ee3c \u0111\u1ea3m b\u1ea3o th\u00f4ng qua kh\u00f3a ngo\u1ea1i kh\u00f4ng?<\/li>\n
                  • Th\u1eeba d\u01b0:<\/strong>C\u00f3 nh\u00f3m d\u1eef li\u1ec7u l\u1eb7p l\u1ea1i r\u00f5 r\u00e0ng n\u00e0o kh\u00f4ng?<\/li>\n
                  • S\u1ed1 l\u01b0\u1ee3ng n\u1ed1i (Join):<\/strong>C\u00e1c truy v\u1ea5n quan tr\u1ecdng c\u00f3 y\u00eau c\u1ea7u nhi\u1ec1u h\u01a1n 3-4 ph\u00e9p n\u1ed1i kh\u00f4ng?<\/li>\n
                  • \u0110\u01b0\u1eddng d\u1eabn c\u1eadp nh\u1eadt:<\/strong>C\u00f3 th\u1ec3 th\u1ef1c hi\u1ec7n thay \u0111\u1ed5i d\u1eef li\u1ec7u duy nh\u1ea5t t\u1ea1i m\u1ed9t v\u1ecb tr\u00ed kh\u00f4ng?<\/li>\n<\/ul>\n

                    \ud83d\udd17 K\u1ebft lu\u1eadn v\u1ec1 ki\u1ebfn tr\u00fac d\u1eef li\u1ec7u<\/h2>\n

                    Chu\u1ea9n h\u00f3a l\u00e0 m\u1ed9t c\u00f4ng c\u1ee5, ch\u1ee9 kh\u00f4ng ph\u1ea3i quy\u1ec3n s\u00e1ch lu\u1eadt l\u1ec7. N\u00f3 t\u1ed3n t\u1ea1i \u0111\u1ec3 b\u1ea3o v\u1ec7 d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n kh\u1ecfi s\u1ef1 kh\u00f4ng nh\u1ea5t qu\u00e1n, nh\u01b0ng kh\u00f4ng n\u00ean ng\u0103n c\u1ea3n \u1ee9ng d\u1ee5ng c\u1ee7a b\u1ea1n ho\u1ea1t \u0111\u1ed9ng hi\u1ec7u qu\u1ea3. S\u1ef1 ‘th\u1eadt’ v\u1ec1 chu\u1ea9n h\u00f3a ERD l\u00e0 n\u00f3 n\u1eb1m tr\u00ean m\u1ed9t thang \u0111\u1ed9. B\u1ea1n b\u1eaft \u0111\u1ea7u v\u1edbi c\u1ea5u tr\u00fac \u0111\u01b0\u1ee3c chu\u1ea9n h\u00f3a cao \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o t\u00ednh to\u00e0n v\u1eb9n, v\u00e0 ch\u1ecdn l\u1ecdc vi\u1ec7c b\u1ecf chu\u1ea9n h\u00f3a d\u1ef1a tr\u00ean nhu c\u1ea7u hi\u1ec7u su\u1ea5t.<\/p>\n

                    Kh\u00f4ng c\u00f3 gi\u1ea3i ph\u00e1p n\u00e0o ph\u00f9 h\u1ee3p v\u1edbi m\u1ecdi t\u00ecnh hu\u1ed1ng. M\u1ed9t h\u1ec7 th\u1ed1ng giao d\u1ecbch t\u1ea7n su\u1ea5t cao s\u1ebd tr\u00f4ng r\u1ea5t kh\u00e1c bi\u1ec7t so v\u1edbi m\u1ed9t h\u1ec7 th\u1ed1ng qu\u1ea3n l\u00fd n\u1ed9i dung. \u0110i\u1ec1u then ch\u1ed1t l\u00e0 hi\u1ec3u r\u00f5 c\u01a1 ch\u1ebf n\u1ec1n t\u1ea3ng c\u1ee7a c\u00e1c ph\u1ee5 thu\u1ed9c v\u00e0 ph\u00e9p n\u1ed1i. B\u1eb1ng c\u00e1ch c\u00e2n b\u1eb1ng chi ph\u00ed l\u01b0u tr\u1eef v\u1edbi chi ph\u00ed t\u00ednh to\u00e1n, b\u1ea1n c\u00f3 th\u1ec3 x\u00e2y d\u1ef1ng c\u00e1c h\u1ec7 th\u1ed1ng v\u1eeba \u0111\u00e1ng tin c\u1eady v\u1eeba nhanh ch\u00f3ng.<\/p>\n

                    Khi b\u1ea1n ti\u1ebfp t\u1ee5c thi\u1ebft k\u1ebf, h\u00e3y nh\u1edb r\u1eb1ng s\u1ef1 ph\u00e1t tri\u1ec3n c\u1ee7a l\u01b0\u1ee3c \u0111\u1ed3 l\u00e0 \u0111i\u1ec1u kh\u00f4ng th\u1ec3 tr\u00e1nh kh\u1ecfi. L\u00ean k\u1ebf ho\u1ea1ch cho nh\u1eefng thay \u0111\u1ed5i. S\u1eed d\u1ee5ng ki\u1ec3m so\u00e1t phi\u00ean b\u1ea3n cho c\u00e1c thao t\u00e1c di chuy\u1ec3n c\u01a1 s\u1edf d\u1eef li\u1ec7u. V\u00e0 lu\u00f4n ki\u1ec3m th\u1eed truy v\u1ea5n c\u1ee7a b\u1ea1n d\u01b0\u1edbi t\u1ea3i tr\u01b0\u1edbc khi \u0111\u01b0a ra quy\u1ebft \u0111\u1ecbnh c\u1ea5u tr\u00fac. L\u01b0\u1ee3c \u0111\u1ed3 t\u1ed1t nh\u1ea5t l\u00e0 l\u01b0\u1ee3c \u0111\u1ed3 h\u1ed7 tr\u1ee3 m\u1ee5c ti\u00eau kinh doanh c\u1ee7a b\u1ea1n m\u00e0 kh\u00f4ng tr\u1edf th\u00e0nh \u0111i\u1ec3m ngh\u1ebdn.<\/p>\n","protected":false},"excerpt":{"rendered":"

                    Thi\u1ebft k\u1ebf m\u1ed9t m\u00f4 h\u00ecnh d\u1eef li\u1ec7u m\u1ea1nh m\u1ebd l\u00e0 m\u1ed9t trong nh\u1eefng nhi\u1ec7m v\u1ee5 quan tr\u1ecdng nh\u1ea5t trong k\u1ef9 thu\u1eadt ph\u1ea7n m\u1ec1m. S\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 (ERD)…<\/p>\n","protected":false},"author":1,"featured_media":1542,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_yoast_wpseo_title":"H\u01b0\u1edbng d\u1eabn chu\u1ea9n h\u00f3a ERD: Khi n\u00e0o n\u00ean d\u1eebng l\u1ea1i ho\u1eb7c b\u1ecf chu\u1ea9n h\u00f3a \ud83d\uddc3\ufe0f","_yoast_wpseo_metadesc":"M\u1ed9t h\u01b0\u1edbng d\u1eabn to\u00e0n di\u1ec7n v\u1ec1 chu\u1ea9n h\u00f3a ERD. H\u1ecdc c\u00e1ch khi n\u00e0o n\u00ean d\u1eebng chu\u1ea9n h\u00f3a v\u00e0 khi n\u00e0o n\u00ean b\u1ecf chu\u1ea9n h\u00f3a \u0111\u1ec3 \u0111\u1ea1t hi\u1ec7u su\u1ea5t v\u00e0 t\u00ednh to\u00e0n v\u1eb9n c\u01a1 s\u1edf d\u1eef li\u1ec7u t\u1ed1i \u01b0u.","fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[88],"tags":[84,87],"class_list":["post-1541","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-erd","tag-academic","tag-erd"],"yoast_head":"\nH\u01b0\u1edbng d\u1eabn chu\u1ea9n h\u00f3a ERD: Khi n\u00e0o n\u00ean d\u1eebng l\u1ea1i ho\u1eb7c b\u1ecf chu\u1ea9n h\u00f3a \ud83d\uddc3\ufe0f<\/title>\n<meta name=\"description\" content=\"M\u1ed9t h\u01b0\u1edbng d\u1eabn to\u00e0n di\u1ec7n v\u1ec1 chu\u1ea9n h\u00f3a ERD. 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