{"id":1704,"date":"2026-04-11T09:40:39","date_gmt":"2026-04-11T09:40:39","guid":{"rendered":"https:\/\/www.viz-note.com\/vi\/erd-normalization-strategies-zero-redundancy-storage\/"},"modified":"2026-04-11T09:40:39","modified_gmt":"2026-04-11T09:40:39","slug":"erd-normalization-strategies-zero-redundancy-storage","status":"publish","type":"post","link":"https:\/\/www.viz-note.com\/vi\/erd-normalization-strategies-zero-redundancy-storage\/","title":{"rendered":"Kh\u00e1m ph\u00e1 s\u00e2u v\u1ec1 c\u00e1c chi\u1ebfn l\u01b0\u1ee3c chu\u1ea9n h\u00f3a s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 nh\u1eb1m l\u01b0u tr\u1eef kh\u00f4ng d\u01b0 th\u1eeba"},"content":{"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 th\u00f4ng tin \u0111\u00e1ng tin c\u1eady n\u00e0o. \u1ede trung t\u00e2m c\u1ee7a thi\u1ebft k\u1ebf n\u00e0y l\u00e0 s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 (ERD), m\u1ed9t b\u1ea3n ph\u00e1c h\u1ecda tr\u1ef1c quan x\u00e1c \u0111\u1ecbnh c\u00e1ch c\u00e1c th\u1ef1c th\u1ec3 d\u1eef li\u1ec7u t\u01b0\u01a1ng t\u00e1c v\u1edbi nhau. Tuy nhi\u00ean, m\u1ed9t s\u01a1 \u0111\u1ed3 \u0111\u01a1n thu\u1ea7n kh\u00f4ng \u0111\u1ea3m b\u1ea3o hi\u1ec7u qu\u1ea3. S\u1ee9c m\u1ea1nh th\u1ef1c s\u1ef1 c\u1ee7a ERD ch\u1ec9 th\u1ec3 hi\u1ec7n khi \u0111\u01b0\u1ee3c k\u1ebft h\u1ee3p v\u1edbi c\u00e1c chi\u1ebfn l\u01b0\u1ee3c chu\u1ea9n h\u00f3a nghi\u00eam ng\u1eb7t. M\u1ee5c ti\u00eau l\u00e0 r\u00f5 r\u00e0ng: \u0111\u1ea1t \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef kh\u00f4ng d\u01b0 th\u1eeba. \u0110i\u1ec1u n\u00e0y c\u00f3 ngh\u0129a l\u00e0 lo\u1ea1i b\u1ecf d\u1eef li\u1ec7u tr\u00f9ng l\u1eb7p \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o t\u00ednh to\u00e0n v\u1eb9n, gi\u1ea3m chi ph\u00ed l\u01b0u tr\u1eef v\u00e0 \u0111\u01a1n gi\u1ea3n h\u00f3a b\u1ea3o tr\u00ec.<\/p>\n

D\u01b0 th\u1eeba kh\u00f4ng ch\u1ec9 l\u00e0 v\u1ea5n \u0111\u1ec1 l\u01b0u tr\u1eef; \u0111\u00f3 l\u00e0 m\u1ed9t l\u1ed7i logic \u0111ang ch\u1edd g\u00e2y ra s\u1ef1 b\u1ea5t nh\u1ea5t. Khi d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c l\u1eb7p l\u1ea1i tr\u00ean nhi\u1ec1u h\u00e0ng ho\u1eb7c b\u1ea3ng m\u00e0 kh\u00f4ng c\u00f3 m\u1ed1i quan h\u1ec7 ch\u1eb7t ch\u1ebd, c\u00e1c b\u1ea5t th\u01b0\u1eddng c\u1eadp nh\u1eadt tr\u1edf n\u00ean kh\u00f4ng th\u1ec3 tr\u00e1nh kh\u1ecfi. M\u1ed9t thay \u0111\u1ed5i trong thu\u1ed9c t\u00ednh duy nh\u1ea5t c\u00f3 th\u1ec3 y\u00eau c\u1ea7u c\u1eadp nh\u1eadt \u1edf h\u00e0ng ch\u1ee5c v\u1ecb tr\u00ed. N\u1ebfu b\u1ecf s\u00f3t m\u1ed9t n\u01a1i n\u00e0o \u0111\u00f3, c\u01a1 s\u1edf d\u1eef li\u1ec7u s\u1ebd b\u1ecb h\u1ecfng. H\u01b0\u1edbng d\u1eabn n\u00e0y kh\u00e1m ph\u00e1 c\u01a1 ch\u1ebf chu\u1ea9n h\u00f3a trong b\u1ed1i c\u1ea3nh thi\u1ebft k\u1ebf ERD, t\u1eadp trung v\u00e0o \u1ee9ng d\u1ee5ng th\u1ef1c ti\u1ec5n v\u00e0 s\u1ef1 thu\u1ea7n khi\u1ebft v\u1ec1 c\u1ea5u tr\u00fac.<\/p>\n

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

\ud83e\uddf1 Hi\u1ec3u r\u00f5 n\u1ec1n t\u1ea3ng c\u1ee7a m\u00f4 h\u00ecnh h\u00f3a d\u1eef li\u1ec7u<\/h2>\n

Tr\u01b0\u1edbc khi \u00e1p d\u1ee5ng c\u00e1c quy t\u1eafc chu\u1ea9n h\u00f3a, c\u1ea7n ph\u1ea3i hi\u1ec3u r\u00f5 c\u00e1c th\u00e0nh ph\u1ea7n c\u1ee7a s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3. M\u1ed9t ERD bao g\u1ed3m c\u00e1c th\u1ef1c th\u1ec3, thu\u1ed9c t\u00ednh v\u00e0 m\u1ed1i quan h\u1ec7. C\u00e1c th\u1ef1c th\u1ec3 \u0111\u1ea1i di\u1ec7n cho c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng ho\u1eb7c kh\u00e1i ni\u1ec7m, ch\u1eb3ng h\u1ea1n nh\u01b0 Kh\u00e1ch h\u00e0ng ho\u1eb7c S\u1ea3n ph\u1ea9m. C\u00e1c thu\u1ed9c t\u00ednh l\u00e0 c\u00e1c \u0111\u1eb7c t\u00ednh m\u00f4 t\u1ea3 c\u00e1c th\u1ef1c th\u1ec3 n\u00e0y, nh\u01b0 T\u00ean ho\u1eb7c Gi\u00e1. C\u00e1c m\u1ed1i quan h\u1ec7 x\u00e1c \u0111\u1ecbnh c\u00e1ch c\u00e1c th\u1ef1c th\u1ec3 k\u1ebft n\u1ed1i v\u1edbi nhau, th\u01b0\u1eddng th\u00f4ng qua kh\u00f3a ngo\u1ea1i.<\/p>\n

Chu\u1ea9n h\u00f3a l\u00e0 qu\u00e1 tr\u00ecnh t\u1ed5 ch\u1ee9c c\u00e1c thu\u1ed9c t\u00ednh n\u00e0y nh\u1eb1m gi\u1ea3m thi\u1ec3u d\u01b0 th\u1eeba v\u00e0 ph\u1ee5 thu\u1ed9c. N\u00f3 bao g\u1ed3m vi\u1ec7c chia c\u00e1c b\u1ea3ng l\u1edbn th\u00e0nh c\u00e1c b\u1ea3ng nh\u1ecf h\u01a1n, c\u00f3 li\u00ean k\u1ebft logic v\u1edbi nhau v\u00e0 x\u00e1c \u0111\u1ecbnh c\u00e1c m\u1ed1i quan h\u1ec7 gi\u1eefa ch\u00fang. M\u1ee5c ti\u00eau l\u00e0 t\u00e1ch bi\u1ec7t d\u1eef li\u1ec7u sao cho m\u1ed7i s\u1ef1 ki\u1ec7n ch\u1ec9 \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef \u1edf m\u1ed9t v\u1ecb tr\u00ed duy nh\u1ea5t.<\/p>\n

H\u00e3y xem s\u1ef1 kh\u00e1c bi\u1ec7t gi\u1eefa c\u00e1ch ti\u1ebfp c\u1eadn kh\u00f4ng chu\u1ea9n h\u00f3a v\u00e0 c\u00e1ch ti\u1ebfp c\u1eadn chu\u1ea9n h\u00f3a. Trong quan \u0111i\u1ec3m kh\u00f4ng chu\u1ea9n h\u00f3a, m\u1ed9t b\u1ea3ng duy nh\u1ea5t c\u00f3 th\u1ec3 l\u01b0u tr\u1eef to\u00e0n b\u1ed9 th\u00f4ng tin v\u1ec1 m\u1ed9t \u0111\u01a1n h\u00e0ng, bao g\u1ed3m \u0111\u1ecba ch\u1ec9 v\u00e0 s\u1ed1 \u0111i\u1ec7n tho\u1ea1i c\u1ee7a kh\u00e1ch h\u00e0ng m\u1ed7i khi \u0111\u1eb7t h\u00e0ng. N\u1ebfu kh\u00e1ch h\u00e0ng chuy\u1ec3n ch\u1ed7, b\u1ea1n ph\u1ea3i c\u1eadp nh\u1eadt t\u1eebng b\u1ea3n ghi \u0111\u01a1n h\u00e0ng. Trong quan \u0111i\u1ec3m chu\u1ea9n h\u00f3a, \u0111\u1ecba ch\u1ec9 kh\u00e1ch h\u00e0ng \u0111\u01b0\u1ee3c l\u01b0u trong m\u1ed9t b\u1ea3ng Kh\u00e1ch h\u00e0ng ri\u00eang bi\u1ec7t. B\u1ea3ng \u0110\u01a1n h\u00e0ng ch\u1ec9 l\u01b0u tham chi\u1ebfu \u0111\u1ebfn ID Kh\u00e1ch h\u00e0ng. S\u1ef1 t\u00e1ch bi\u1ec7t n\u00e0y ch\u00ednh l\u00e0 c\u1ed1t l\u00f5i c\u1ee7a vi\u1ec7c kh\u00f4ng d\u01b0 th\u1eeba.<\/p>\n

\ud83d\udcc9 Nh\u1eefng r\u1ee7i ro t\u1eeb d\u1eef li\u1ec7u kh\u00f4ng \u0111\u01b0\u1ee3c chu\u1ea9n h\u00f3a<\/h2>\n

T\u1ea1i sao vi\u1ec7c kh\u00f4ng d\u01b0 th\u1eeba l\u1ea1i quan tr\u1ecdng \u0111\u1ebfn v\u1eady? C\u00e2u tr\u1ea3 l\u1eddi n\u1eb1m \u1edf c\u00e1c lo\u1ea1i b\u1ea5t th\u01b0\u1eddng x\u1ea3y ra khi b\u1ecf qua chu\u1ea9n h\u00f3a. Nh\u1eefng b\u1ea5t th\u01b0\u1eddng n\u00e0y \u0111e d\u1ecda \u0111\u1ebfn \u0111\u1ed9 tin c\u1eady c\u1ee7a to\u00e0n b\u1ed9 h\u1ec7 th\u1ed1ng.<\/p>\n

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  • B\u1ea5t th\u01b0\u1eddng ch\u00e8n d\u1eef li\u1ec7u:<\/strong>B\u1ea1n kh\u00f4ng th\u1ec3 th\u00eam d\u1eef li\u1ec7u cho m\u1ed9t th\u1ef1c th\u1ec3 m\u00e0 kh\u00f4ng th\u00eam d\u1eef li\u1ec7u cho th\u1ef1c th\u1ec3 kh\u00e1c. V\u00ed d\u1ee5, n\u1ebfu m\u1ed9t nh\u00e2n vi\u00ean m\u1edbi ch\u01b0a \u0111\u01b0\u1ee3c g\u00e1n v\u00e0o d\u1ef1 \u00e1n n\u00e0o, b\u1ea1n c\u00f3 th\u1ec3 kh\u00f4ng th\u1ec3 ghi nh\u1eadn s\u1ef1 t\u1ed3n t\u1ea1i c\u1ee7a h\u1ecd n\u1ebfu b\u1ea3ng y\u00eau c\u1ea7u ID d\u1ef1 \u00e1n.<\/li>\n
  • B\u1ea5t th\u01b0\u1eddng x\u00f3a d\u1eef li\u1ec7u:<\/strong>Vi\u1ec7c x\u00f3a d\u1eef li\u1ec7u cho m\u1ed9t th\u1ef1c th\u1ec3 c\u00f3 th\u1ec3 v\u00f4 t\u00ecnh x\u00f3a d\u1eef li\u1ec7u cho th\u1ef1c th\u1ec3 kh\u00e1c. N\u1ebfu b\u1ea1n x\u00f3a \u0111\u01a1n h\u00e0ng cu\u1ed1i c\u00f9ng c\u1ee7a m\u1ed9t kh\u00e1ch h\u00e0ng, b\u1ea1n c\u00f3 th\u1ec3 m\u1ea5t ho\u00e0n to\u00e0n th\u00f4ng tin li\u00ean h\u1ec7 c\u1ee7a kh\u00e1ch h\u00e0ng \u0111\u00f3.<\/li>\n
  • B\u1ea5t th\u01b0\u1eddng c\u1eadp nh\u1eadt:<\/strong>\u0110\u00e2y l\u00e0 v\u1ea5n \u0111\u1ec1 ph\u1ed5 bi\u1ebfn nh\u1ea5t. N\u1ebfu \u0111\u1ecba ch\u1ec9 kh\u00e1ch h\u00e0ng \u0111\u01b0\u1ee3c l\u01b0u trong nhi\u1ec1u b\u1ea3n ghi \u0111\u01a1n h\u00e0ng, vi\u1ec7c c\u1eadp nh\u1eadt \u0111\u1ecba ch\u1ec9 \u0111\u00f2i h\u1ecfi ph\u1ea3i t\u00ecm v\u00e0 thay \u0111\u1ed5i t\u1eebng b\u1ea3n ghi m\u1ed9t. Vi\u1ec7c b\u1ecf s\u00f3t s\u1ebd d\u1eabn \u0111\u1ebfn d\u1eef li\u1ec7u m\u00e2u thu\u1eabn.<\/li>\n<\/ul>\n

    \u0110\u1ea1t \u0111\u01b0\u1ee3c kh\u00f4ng d\u01b0 th\u1eeba tr\u1ef1c ti\u1ebfp gi\u1ea3m thi\u1ec3u nh\u1eefng r\u1ee7i ro n\u00e0y. B\u1eb1ng c\u00e1ch \u0111\u1ea3m b\u1ea3o m\u1ed7i m\u1ea3nh th\u00f4ng tin ch\u1ec9 c\u00f3 m\u1ed9t n\u01a1i l\u01b0u tr\u1eef duy nh\u1ea5t, h\u1ec7 th\u1ed1ng tr\u1edf n\u00ean t\u1ef1 \u0111i\u1ec1u ch\u1ec9nh. C\u00e1c thay \u0111\u1ed5i ch\u1ec9 x\u1ea3y ra m\u1ed9t l\u1ea7n, v\u00e0 thay \u0111\u1ed5i \u0111\u01b0\u1ee3c lan truy\u1ec1n m\u1ed9t c\u00e1ch h\u1ee3p l\u00fd th\u00f4ng qua c\u00e1c m\u1ed1i quan h\u1ec7.<\/p>\n

    \ud83e\ude9c Con \u0111\u01b0\u1eddng d\u1eabn \u0111\u1ebfn c\u00e1c d\u1ea1ng chu\u1ea9n h\u00f3a<\/h2>\n

    Chu\u1ea9n h\u00f3a kh\u00f4ng ph\u1ea3i l\u00e0 m\u1ed9t b\u01b0\u1edbc duy nh\u1ea5t m\u00e0 l\u00e0 m\u1ed9t qu\u00e1 tr\u00ecnh ti\u1ebfn tri\u1ec3n qua c\u00e1c giai \u0111o\u1ea1n ri\u00eang bi\u1ec7t g\u1ecdi l\u00e0 C\u00e1c d\u1ea1ng chu\u1ea9n h\u00f3a. M\u1ed7i d\u1ea1ng gi\u1ea3i quy\u1ebft c\u00e1c lo\u1ea1i d\u01b0 th\u1eeba c\u1ee5 th\u1ec3. M\u1eb7c d\u00f9 c\u00e1c m\u00f4 h\u00ecnh l\u00fd thuy\u1ebft c\u00f3 th\u1ec3 \u0111i \u0111\u1ebfn D\u1ea1ng chu\u1ea9n h\u00f3a th\u1ee9 N\u0103m (5NF), thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u th\u1ef1c t\u1ebf th\u01b0\u1eddng t\u1eadp trung v\u00e0o ba d\u1ea1ng \u0111\u1ea7u ti\u00ean v\u00e0 D\u1ea1ng chu\u1ea9n h\u00f3a Boyce-Codd (BCNF).<\/p>\n

    1\ufe0f\u20e3 D\u1ea1ng chu\u1ea9n h\u00f3a th\u1ee9 nh\u1ea5t (1NF)<\/h3>\n

    Quy t\u1eafc \u0111\u1ea7u ti\u00ean c\u1ee7a chu\u1ea9n h\u00f3a l\u00e0 \u0111\u1ea3m b\u1ea3o t\u00ednh nguy\u00ean t\u1eed. M\u1ed9t b\u1ea3ng \u1edf d\u1ea1ng 1NF n\u1ebfu n\u00f3 kh\u00f4ng ch\u1ee9a nh\u00f3m l\u1eb7p l\u1ea1i hay m\u1ea3ng. M\u1ed7i c\u1ed9t ph\u1ea3i ch\u1ee9a m\u1ed9t gi\u00e1 tr\u1ecb duy nh\u1ea5t, v\u00e0 m\u1ed7i h\u00e0ng ph\u1ea3i l\u00e0 duy nh\u1ea5t.<\/p>\n

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    • Gi\u00e1 tr\u1ecb nguy\u00ean t\u1eed:<\/strong>M\u1ed9t tr\u01b0\u1eddng kh\u00f4ng th\u1ec3 ch\u1ee9a danh s\u00e1ch c\u00e1c gi\u00e1 tr\u1ecb. Thay v\u00ec m\u1ed9t c\u1ed9t t\u00ean l\u00e0 \u201cK\u1ef9 n\u0103ng\u201d ch\u1ee9a \u201cJava, SQL, Python\u201d, b\u1ea1n n\u00ean t\u1ea1o c\u00e1c h\u00e0ng ri\u00eang bi\u1ec7t cho t\u1eebng k\u1ef9 n\u0103ng ho\u1eb7c m\u1ed9t b\u1ea3ng ri\u00eang cho k\u1ef9 n\u0103ng.<\/li>\n
    • C\u00e1c h\u00e0ng duy nh\u1ea5t:<\/strong>M\u1ed7i h\u00e0ng ph\u1ea3i ph\u00e2n bi\u1ec7t \u0111\u01b0\u1ee3c v\u1edbi m\u1ecdi h\u00e0ng kh\u00e1c. \u0110i\u1ec1u n\u00e0y th\u01b0\u1eddng y\u00eau c\u1ea7u c\u00f3 Kh\u00f3a ch\u00ednh.<\/li>\n<\/ul>\n

      Trong b\u1ed1i c\u1ea3nh ERD, \u0111i\u1ec1u n\u00e0y c\u00f3 ngh\u0129a l\u00e0 ki\u1ec3m tra t\u1eebng thu\u1ed9c t\u00ednh. N\u1ebfu m\u1ed9t thu\u1ed9c t\u00ednh m\u00f4 t\u1ea3 m\u1ed9t thu\u1ed9c t\u00ednh \u0111a gi\u00e1 tr\u1ecb, n\u00f3 ph\u1ea3i \u0111\u01b0\u1ee3c t\u00e1ch ra. \u0110\u00e2y l\u00e0 b\u01b0\u1edbc n\u1ec1n t\u1ea3ng. Kh\u00f4ng c\u00f3 1NF, c\u00e1c d\u1ea1ng cao h\u01a1n kh\u00f4ng th\u1ec3 \u0111\u01b0\u1ee3c \u00e1p d\u1ee5ng hi\u1ec7u qu\u1ea3.<\/p>\n

      2\ufe0f\u20e3 D\u1ea1ng chu\u1ea9n h\u00f3a th\u1ee9 hai (2NF)<\/h3>\n

      M\u1ed9t khi b\u1ea3ng \u0111\u00e3 \u1edf d\u1ea1ng 1NF, n\u00f3 ph\u1ea3i \u0111\u00e1p \u1ee9ng c\u00e1c ti\u00eau ch\u00ed c\u1ee7a 2NF. M\u1ed9t b\u1ea3ng \u1edf d\u1ea1ng 2NF n\u1ebfu n\u00f3 \u1edf d\u1ea1ng 1NF v\u00e0 t\u1ea5t c\u1ea3 c\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng kh\u00f3a \u0111\u1ec1u ph\u1ee5 thu\u1ed9c ho\u00e0n to\u00e0n v\u00e0o to\u00e0n b\u1ed9 kh\u00f3a ch\u00ednh.<\/p>\n

      Quy t\u1eafc n\u00e0y ch\u1ee7 y\u1ebfu gi\u1ea3i quy\u1ebft c\u00e1c b\u1ea3ng c\u00f3 kh\u00f3a h\u1ee3p th\u00e0nh (kh\u00f3a g\u1ed3m nhi\u1ec1u c\u1ed9t). N\u1ebfu m\u1ed9t b\u1ea3ng c\u00f3 kh\u00f3a h\u1ee3p th\u00e0nh, m\u1ecdi thu\u1ed9c t\u00ednh ph\u1ea3i ph\u1ee5 thu\u1ed9c v\u00e0o to\u00e0n b\u1ed9 kh\u00f3a, ch\u1ee9 kh\u00f4ng ch\u1ec9 m\u1ed9t ph\u1ea7n c\u1ee7a n\u00f3.<\/p>\n

        \n
      • Ph\u1ee5 thu\u1ed9c ho\u00e0n to\u00e0n:<\/strong>N\u1ebfu m\u1ed9t c\u1ed9t ch\u1ec9 ph\u1ee5 thu\u1ed9c v\u00e0o m\u1ed9t ph\u1ea7n c\u1ee7a kh\u00f3a h\u1ee3p th\u00e0nh, th\u00ec n\u00f3 thu\u1ed9c v\u1ec1 m\u1ed9t b\u1ea3ng ri\u00eang bi\u1ec7t.<\/li>\n
      • Ph\u1ee5 thu\u1ed9c t\u1eebng ph\u1ea7n:<\/strong> \u0110\u00e2y l\u00e0 lo\u1ea1i d\u01b0 th\u1eeba c\u1ee5 th\u1ec3 m\u00e0 d\u1ea1ng chu\u1ea9n 2NF lo\u1ea1i b\u1ecf. V\u00ed d\u1ee5, trong m\u1ed9t b\u1ea3ng li\u00ean k\u1ebft gi\u1eefa Sinh vi\u00ean v\u00e0 Kh\u00f3a h\u1ecdc, n\u1ebfu l\u01b0u tr\u1eef “T\u00ean sinh vi\u00ean”, th\u00ec n\u00f3 ch\u1ec9 ph\u1ee5 thu\u1ed9c v\u00e0o M\u00e3 sinh vi\u00ean, ch\u1ee9 kh\u00f4ng ph\u1ee5 thu\u1ed9c v\u00e0o M\u00e3 kh\u00f3a h\u1ecdc. \u0110i\u1ec1u n\u00e0y t\u1ea1o ra s\u1ef1 d\u01b0 th\u1eeba.<\/li>\n<\/ul>\n

        Gi\u1ea3i quy\u1ebft v\u1ea5n \u0111\u1ec1 n\u00e0y \u0111\u00f2i h\u1ecfi vi\u1ec7c chia b\u1ea3ng th\u00e0nh c\u00e1c b\u1ea3ng nh\u1ecf h\u01a1n. B\u1ea1n t\u1ea1o m\u1ed9t b\u1ea3ng Sinh vi\u00ean v\u00e0 m\u1ed9t b\u1ea3ng Kh\u00f3a h\u1ecdc, v\u1edbi m\u1ed9t b\u1ea3ng li\u00ean k\u1ebft (junction table) k\u1ebft n\u1ed1i ch\u00fang. \u0110i\u1ec1u n\u00e0y \u0111\u1ea3m b\u1ea3o r\u1eb1ng th\u00f4ng tin sinh vi\u00ean kh\u00f4ng b\u1ecb l\u1eb7p l\u1ea1i cho m\u1ed7i kh\u00f3a h\u1ecdc m\u00e0 h\u1ecd tham gia.<\/p>\n

        3\ufe0f\u20e3 D\u1ea1ng chu\u1ea9n th\u1ee9 ba (3NF)<\/h3>\n

        D\u1ea1ng chu\u1ea9n th\u1ee9 ba x\u1eed l\u00fd c\u00e1c ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u. M\u1ed9t b\u1ea3ng \u1edf d\u1ea1ng 3NF n\u1ebfu n\u00f3 \u1edf d\u1ea1ng 2NF v\u00e0 kh\u00f4ng c\u00f3 thu\u1ed9c t\u00ednh kh\u00f4ng kh\u00f3a n\u00e0o ph\u1ee5 thu\u1ed9c v\u00e0o m\u1ed9t thu\u1ed9c t\u00ednh kh\u00f4ng kh\u00f3a kh\u00e1c.<\/p>\n

        N\u00f3i m\u1ed9t c\u00e1ch \u0111\u01a1n gi\u1ea3n, c\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng n\u00ean ph\u1ee5 thu\u1ed9c v\u00e0o c\u00e1c thu\u1ed9c t\u00ednh kh\u00e1c kh\u00f4ng thu\u1ed9c kh\u00f3a ch\u00ednh. \u0110i\u1ec1u n\u00e0y th\u01b0\u1eddng x\u1ea3y ra khi m\u1ed9t c\u1ed9t m\u00f4 t\u1ea3 m\u1ed9t c\u1ed9t kh\u00e1c thay v\u00ec m\u00f4 t\u1ea3 ch\u00ednh b\u1ea3n ghi.<\/p>\n

          \n
        • Ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u:<\/strong> N\u1ebfu A x\u00e1c \u0111\u1ecbnh B, v\u00e0 B x\u00e1c \u0111\u1ecbnh C, th\u00ec A x\u00e1c \u0111\u1ecbnh C. N\u1ebfu B kh\u00f4ng ph\u1ea3i l\u00e0 kh\u00f3a, th\u00ec C s\u1ebd \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef m\u1ed9t c\u00e1ch d\u01b0 th\u1eeba.<\/li>\n
        • V\u00ed d\u1ee5:<\/strong> Trong m\u1ed9t b\u1ea3ng Nh\u00e2n vi\u00ean, n\u1ebfu b\u1ea1n l\u01b0u tr\u1eef “T\u00ean ph\u00f2ng ban” v\u00e0 “Tr\u01b0\u1edfng ph\u00f2ng”, th\u00ec Tr\u01b0\u1edfng ph\u00f2ng ph\u1ee5 thu\u1ed9c v\u00e0o T\u00ean ph\u00f2ng ban. N\u1ebfu t\u00ean ph\u00f2ng ban thay \u0111\u1ed5i, c\u1ed9t Tr\u01b0\u1edfng ph\u00f2ng c\u00f3 th\u1ec3 tr\u1edf n\u00ean kh\u00f4ng nh\u1ea5t qu\u00e1n n\u1ebfu kh\u00f4ng \u0111\u01b0\u1ee3c qu\u1ea3n l\u00fd c\u1ea9n th\u1eadn.<\/li>\n<\/ul>\n

          \u0110\u1ec3 kh\u1eafc ph\u1ee5c \u0111i\u1ec1u n\u00e0y, h\u00e3y di chuy\u1ec3n th\u00f4ng tin ph\u00f2ng ban sang m\u1ed9t b\u1ea3ng Ph\u00f2ng ban ri\u00eang bi\u1ec7t. B\u1ea3ng Nh\u00e2n vi\u00ean sau \u0111\u00f3 ch\u1ec9 l\u01b0u m\u00e3 Ph\u00f2ng ban. \u0110i\u1ec1u n\u00e0y t\u00e1ch bi\u1ec7t d\u1eef li\u1ec7u ph\u00f2ng ban, \u0111\u1ea3m b\u1ea3o r\u1eb1ng n\u1ebfu m\u1ed9t ph\u00f2ng ban \u0111\u01b0\u1ee3c \u0111\u1ed5i t\u00ean, b\u1ea1n ch\u1ec9 c\u1ea7n c\u1eadp nh\u1eadt \u1edf m\u1ed9t n\u01a1i.<\/p>\n

          4\ufe0f\u20e3 D\u1ea1ng chu\u1ea9n Boyce-Codd (BCNF)<\/h3>\n

          BCNF l\u00e0 phi\u00ean b\u1ea3n nghi\u00eam ng\u1eb7t h\u01a1n c\u1ee7a 3NF. N\u00f3 \u00e1p d\u1ee5ng khi c\u00f3 nhi\u1ec1u kh\u00f3a kh\u1ea3 d\u1ee5ng ho\u1eb7c khi m\u1ed9t thu\u1ed9c t\u00ednh kh\u00f4ng kh\u00f3a x\u00e1c \u0111\u1ecbnh m\u1ed9t thu\u1ed9c t\u00ednh kh\u00f4ng kh\u00f3a kh\u00e1c theo m\u1ed9t c\u00e1ch c\u1ee5 th\u1ec3. M\u1ed9t b\u1ea3ng \u1edf d\u1ea1ng BCNF n\u1ebfu v\u1edbi m\u1ecdi ph\u1ee5 thu\u1ed9c h\u00e0m X \u2192 Y, th\u00ec X l\u00e0 si\u00eau kh\u00f3a.<\/p>\n

          D\u1ea1ng n\u00e0y x\u1eed l\u00fd c\u00e1c t\u00ecnh hu\u1ed1ng ph\u1ee9c t\u1ea1p m\u00e0 3NF v\u1eabn c\u00f3 th\u1ec3 cho ph\u00e9p c\u00e1c b\u1ea5t th\u01b0\u1eddng. N\u00f3 \u0111\u1ea3m b\u1ea3o r\u1eb1ng m\u1ecdi y\u1ebfu t\u1ed1 x\u00e1c \u0111\u1ecbnh \u0111\u1ec1u l\u00e0 kh\u00f3a kh\u1ea3 d\u1ee5ng. M\u1eb7c d\u00f9 kh\u00f4ng ph\u1ea3i l\u00fac n\u00e0o c\u0169ng c\u1ea7n thi\u1ebft cho m\u1ecdi l\u01b0\u1ee3c \u0111\u1ed3, nh\u01b0ng h\u01b0\u1edbng t\u1edbi BCNF mang l\u1ea1i m\u1ee9c \u0111\u1ed9 to\u00e0n v\u1eb9n c\u1ea5u tr\u00fac cao nh\u1ea5t cho vi\u1ec7c lo\u1ea1i b\u1ecf ho\u00e0n to\u00e0n d\u01b0 th\u1eeba.<\/p>\n

          \ud83d\udee0\ufe0f X\u1eed l\u00fd c\u00e1c b\u1ea5t th\u01b0\u1eddng: M\u1ed9t c\u00e1i nh\u00ecn so s\u00e1nh<\/h2>\n

          Hi\u1ec3u \u0111\u01b0\u1ee3c t\u00e1c \u0111\u1ed9ng c\u1ee7a chu\u1ea9n h\u00f3a \u0111\u00f2i h\u1ecfi m\u1ed9t c\u00e1i nh\u00ecn r\u00f5 r\u00e0ng v\u1ec1 c\u00e1ch c\u00e1c b\u1ea5t th\u01b0\u1eddng th\u1ec3 hi\u1ec7n ra. B\u1ea3ng d\u01b0\u1edbi \u0111\u00e2y n\u00eau b\u1eadt s\u1ef1 kh\u00e1c bi\u1ec7t gi\u1eefa tr\u1ea1ng th\u00e1i \u0111\u00e3 chu\u1ea9n h\u00f3a v\u00e0 ch\u01b0a chu\u1ea9n h\u00f3a li\u00ean quan \u0111\u1ebfn c\u00e1c v\u1ea5n \u0111\u1ec1 d\u1eef li\u1ec7u ph\u1ed5 bi\u1ebfn.<\/p>\n\n\n\n\n\n\n\n\n
          Lo\u1ea1i b\u1ea5t th\u01b0\u1eddng<\/th>\nTr\u1ea1ng th\u00e1i ch\u01b0a chu\u1ea9n h\u00f3a<\/th>\nTr\u1ea1ng th\u00e1i \u0111\u00e3 chu\u1ea9n h\u00f3a (kh\u00f4ng d\u01b0 th\u1eeba)<\/th>\n<\/tr>\n<\/thead>\n
          C\u1eadp nh\u1eadt<\/strong><\/td>\nY\u00eau c\u1ea7u thay \u0111\u1ed5i d\u1eef li\u1ec7u \u1edf nhi\u1ec1u h\u00e0ng. Nguy c\u01a1 cao v\u1ec1 s\u1ef1 kh\u00f4ng nh\u1ea5t qu\u00e1n.<\/td>\nCh\u1ec9 y\u00eau c\u1ea7u thay \u0111\u1ed5i d\u1eef li\u1ec7u \u1edf m\u1ed9t h\u00e0ng. T\u00ednh nh\u1ea5t qu\u00e1n \u0111\u01b0\u1ee3c \u0111\u1ea3m b\u1ea3o t\u1ef1 \u0111\u1ed9ng.<\/td>\n<\/tr>\n
          Ch\u00e8n d\u1eef li\u1ec7u<\/strong><\/td>\nC\u00f3 th\u1ec3 y\u00eau c\u1ea7u d\u1eef li\u1ec7u gi\u1ea3 \u0111\u1ec3 \u0111\u00e1p \u1ee9ng c\u00e1c r\u00e0ng bu\u1ed9c kh\u00f3a ngo\u1ea1i.<\/td>\nC\u00e1c th\u1ef1c th\u1ec3 m\u1edbi c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c th\u00eam v\u00e0o \u0111\u1ed9c l\u1eadp m\u00e0 kh\u00f4ng c\u1ea7n d\u1eef li\u1ec7u li\u00ean quan.<\/td>\n<\/tr>\n
          X\u00f3a<\/strong><\/td>\nVi\u1ec7c x\u00f3a m\u1ed9t b\u1ea3n ghi c\u00f3 th\u1ec3 x\u00f3a \u0111i d\u1eef li\u1ec7u thi\u1ebft y\u1ebfu v\u1ec1 m\u1ed9t th\u1ef1c th\u1ec3 kh\u00e1c.<\/td>\nVi\u1ec7c x\u00f3a m\u1ed9t b\u1ea3n ghi ch\u1ec9 \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn th\u1ef1c th\u1ec3 c\u1ee5 th\u1ec3 \u0111\u00f3, b\u1ea3o to\u00e0n c\u00e1c th\u1ef1c th\u1ec3 kh\u00e1c.<\/td>\n<\/tr>\n
          B\u1ed9 nh\u1edb l\u01b0u tr\u1eef<\/strong><\/td>\nTi\u00eau th\u1ee5 b\u1ed9 nh\u1edb cao do c\u00e1c chu\u1ed7i v\u00e0 gi\u00e1 tr\u1ecb b\u1ecb l\u1eb7p l\u1ea1i.<\/td>\nS\u1eed d\u1ee5ng b\u1ed9 nh\u1edb t\u1ed1i thi\u1ec3u; c\u00e1c gi\u00e1 tr\u1ecb \u0111\u01b0\u1ee3c tham chi\u1ebfu th\u00f4ng qua ID.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

          Nh\u01b0 \u0111\u00e3 th\u1ea5y, ph\u01b0\u01a1ng ph\u00e1p chu\u1ea9n h\u00f3a gi\u1ea3m \u0111\u00e1ng k\u1ec3 g\u00e1nh n\u1eb7ng v\u1eadn h\u00e0nh trong qu\u1ea3n l\u00fd d\u1eef li\u1ec7u. Chi ph\u00ed l\u00e0 truy v\u1ea5n ph\u1ee9c t\u1ea1p h\u01a1n m\u1ed9t ch\u00fat, do c\u1ea7n th\u1ef1c hi\u1ec7n c\u00e1c ph\u00e9p n\u1ed1i \u0111\u1ec3 truy xu\u1ea5t th\u00f4ng tin \u0111\u1ea7y \u0111\u1ee7. Tuy nhi\u00ean, s\u1ef1 \u0111\u00e1nh \u0111\u1ed5i n\u00e0y l\u1ea1i c\u00f3 l\u1ee3i cho t\u00ednh to\u00e0n v\u1eb9n v\u00e0 kh\u1ea3 n\u0103ng b\u1ea3o tr\u00ec l\u00e2u d\u00e0i.<\/p>\n

          \ud83d\udee0\ufe0f C\u00e1c chi\u1ebfn l\u01b0\u1ee3c tri\u1ec3n khai<\/h2>\n

          Tri\u1ec3n khai c\u00e1c chi\u1ebfn l\u01b0\u1ee3c n\u00e0y trong giai \u0111o\u1ea1n thi\u1ebft k\u1ebf s\u01a1 \u0111\u1ed3 ERD l\u00e0 \u0111i\u1ec1u r\u1ea5t quan tr\u1ecdng. Vi\u1ec7c ng\u0103n ng\u1eeba s\u1ef1 tr\u00f9ng l\u1eb7p d\u1eef li\u1ec7u d\u1ec5 h\u01a1n r\u1ea5t nhi\u1ec1u so v\u1edbi vi\u1ec7c s\u1eeda ch\u1eefa sau khi d\u1eef li\u1ec7u \u0111\u00e3 \u0111\u01b0\u1ee3c \u0111i\u1ec1n \u0111\u1ea7y. D\u01b0\u1edbi \u0111\u00e2y l\u00e0 c\u00e1c b\u01b0\u1edbc h\u00e0nh \u0111\u1ed9ng c\u1ee5 th\u1ec3 d\u00e0nh cho c\u00e1c nh\u00e0 thi\u1ebft k\u1ebf.<\/p>\n

          1. X\u00e1c \u0111\u1ecbnh c\u00e1c ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng s\u1edbm<\/h3>\n

          Tr\u01b0\u1edbc khi v\u1ebd c\u00e1c \u0111\u01b0\u1eddng n\u1ed1i gi\u1eefa c\u00e1c th\u1ef1c th\u1ec3, h\u00e3y li\u1ec7t k\u00ea c\u00e1c thu\u1ed9c t\u00ednh v\u00e0 x\u00e1c \u0111\u1ecbnh c\u00e1i n\u00e0o quy\u1ebft \u0111\u1ecbnh c\u00e1i n\u00e0o. N\u1ebfu b\u1ea1n bi\u1ebft r\u1eb1ng Thu\u1ed9c t\u00ednh A quy\u1ebft \u0111\u1ecbnh Thu\u1ed9c t\u00ednh B, th\u00ec b\u1ea1n s\u1ebd bi\u1ebft ch\u00fang c\u00f3 kh\u1ea3 n\u0103ng cao n\u00ean n\u1eb1m trong c\u00f9ng m\u1ed9t th\u1ef1c th\u1ec3, tr\u1eeb khi A kh\u00f4ng ph\u1ea3i l\u00e0 kh\u00f3a.<\/p>\n

            \n
          • X\u00e1c \u0111\u1ecbnh t\u1ea5t c\u1ea3 c\u00e1c m\u1ed1i quan h\u1ec7.<\/li>\n
          • H\u1ecfi: \u201cThu\u1ed9c t\u00ednh n\u00e0y c\u00f3 ph\u1ee5 thu\u1ed9c v\u00e0o to\u00e0n b\u1ed9 kh\u00f3a kh\u00f4ng?\u201d<\/li>\n
          • H\u1ecfi: \u201cThu\u1ed9c t\u00ednh n\u00e0y c\u00f3 ph\u1ee5 thu\u1ed9c v\u00e0o m\u1ed9t thu\u1ed9c t\u00ednh kh\u00f4ng kh\u00f3a kh\u00e1c kh\u00f4ng?\u201d<\/li>\n<\/ul>\n

            2. T\u00e1ch bi\u1ec7t c\u00e1c th\u1ef1c th\u1ec3 d\u1ef1a tr\u00ean v\u00f2ng \u0111\u1eddi<\/h3>\n

            C\u00e1c th\u1ef1c th\u1ec3 c\u00f3 t\u1ea7n su\u1ea5t c\u1eadp nh\u1eadt kh\u00e1c nhau th\u01b0\u1eddng n\u00ean \u0111\u01b0\u1ee3c t\u00e1ch bi\u1ec7t. N\u1ebfu m\u1ed9t b\u1ea3ng tham chi\u1ebfu t\u0129nh (v\u00ed d\u1ee5 nh\u01b0 danh s\u00e1ch c\u00e1c qu\u1ed1c gia) \u0111\u01b0\u1ee3c g\u1ed9p chung v\u1edbi m\u1ed9t b\u1ea3ng giao d\u1ecbch (v\u00ed d\u1ee5 nh\u01b0 \u0111\u01a1n h\u00e0ng), d\u1eef li\u1ec7u t\u0129nh s\u1ebd t\u1ea1o ra s\u1ef1 tr\u00f9ng l\u1eb7p kh\u00f4ng c\u1ea7n thi\u1ebft trong b\u1ea3ng giao d\u1ecbch.<\/p>\n

            3. S\u1eed d\u1ee5ng kh\u00f3a gi\u1ea3<\/h3>\n

            Thay v\u00ec s\u1eed d\u1ee5ng d\u1eef li\u1ec7u t\u1ef1 nhi\u00ean l\u00e0m kh\u00f3a ch\u00ednh, h\u00e3y c\u00e2n nh\u1eafc s\u1eed d\u1ee5ng kh\u00f3a gi\u1ea3 (m\u1ed9t \u0111\u1ecbnh danh duy nh\u1ea5t do h\u1ec7 th\u1ed1ng t\u1ea1o ra). \u0110i\u1ec1u n\u00e0y ng\u0103n ng\u1eeba c\u00e1c v\u1ea5n \u0111\u1ec1 x\u1ea3y ra khi ch\u00ednh kh\u00f3a thay \u0111\u1ed5i theo th\u1eddi gian, \u0111i\u1ec1u \u0111\u00f3 s\u1ebd l\u00e0m h\u1ecfng c\u00e1c m\u1ed1i quan h\u1ec7 trong h\u1ec7 th\u1ed1ng \u0111\u00e3 \u0111\u01b0\u1ee3c chu\u1ea9n h\u00f3a.<\/p>\n

            4. X\u00e1c minh b\u1eb1ng d\u1eef li\u1ec7u ki\u1ec3m th\u1eed<\/h3>\n

            Tr\u01b0\u1edbc khi ho\u00e0n t\u1ea5t s\u01a1 \u0111\u1ed3 ERD, h\u00e3y th\u1eed \u0111i\u1ec1n d\u1eef li\u1ec7u m\u1eabu v\u00e0o n\u00f3. H\u00e3y th\u1eed t\u1ea1o ra c\u00e1c hi\u1ec7n t\u01b0\u1ee3ng b\u1ea5t th\u01b0\u1eddng \u0111\u01b0\u1ee3c m\u00f4 t\u1ea3 tr\u01b0\u1edbc \u0111\u00f3. N\u1ebfu b\u1ea1n c\u00f3 th\u1ec3 ch\u00e8n m\u1ed9t kh\u00e1ch h\u00e0ng m\u00e0 kh\u00f4ng c\u1ea7n \u0111\u01a1n h\u00e0ng, v\u00e0 x\u00f3a m\u1ed9t \u0111\u01a1n h\u00e0ng m\u00e0 kh\u00f4ng l\u00e0m m\u1ea5t kh\u00e1ch h\u00e0ng, th\u00ec thi\u1ebft k\u1ebf c\u1ee7a b\u1ea1n c\u00f3 kh\u1ea3 n\u0103ng l\u00e0 h\u1ee3p l\u00fd.<\/p>\n

            \u2696\ufe0f C\u00e2n b\u1eb1ng hi\u1ec7u su\u1ea5t v\u00e0 \u0111\u1ed9 thu\u1ea7n khi\u1ebft<\/h2>\n

            \u0110\u1ea1t \u0111\u01b0\u1ee3c kh\u00f4ng c\u00f3 tr\u00f9ng l\u1eb7p d\u1eef li\u1ec7u kh\u00f4ng c\u00f3 ngh\u0129a l\u00e0 t\u1ed1i \u0111a h\u00f3a s\u1ed1 l\u01b0\u1ee3ng b\u1ea3ng. Chu\u1ea9n h\u00f3a qu\u00e1 m\u1ee9c c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn suy gi\u1ea3m hi\u1ec7u su\u1ea5t. Khi m\u1ed9t truy v\u1ea5n y\u00eau c\u1ea7u d\u1eef li\u1ec7u t\u1eeb m\u01b0\u1eddi b\u1ea3ng kh\u00e1c nhau, h\u1ec7 th\u1ed1ng ph\u1ea3i th\u1ef1c hi\u1ec7n m\u01b0\u1eddi ph\u00e9p n\u1ed1i. \u0110i\u1ec1u n\u00e0y c\u00f3 th\u1ec3 l\u00e0m ch\u1eadm \u0111\u00e1ng k\u1ec3 c\u00e1c thao t\u00e1c \u0111\u1ecdc.<\/p>\n

            Khi n\u00e0o n\u00ean kh\u00f4ng chu\u1ea9n h\u00f3a<\/h3>\n

            C\u00f3 nh\u1eefng l\u00fd do h\u1ee3p l\u00fd \u0111\u1ec3 ch\u1ee7 \u00fd \u0111\u01b0a l\u1ea1i s\u1ef1 tr\u00f9ng l\u1eb7p d\u1eef li\u1ec7u. \u0110i\u1ec1u n\u00e0y th\u01b0\u1eddng \u0111\u01b0\u1ee3c g\u1ecdi l\u00e0 kh\u00f4ng chu\u1ea9n h\u00f3a.<\/p>\n

              \n
            • H\u1ec7 th\u1ed1ng tr\u1ecdng t\u1ea3i \u0111\u1ecdc cao:<\/strong> Trong c\u00e1c kho d\u1eef li\u1ec7u ho\u1eb7c c\u00f4ng c\u1ee5 b\u00e1o c\u00e1o, t\u1ed1c \u0111\u1ed9 \u0111\u1ecdc \u0111\u01b0\u1ee3c \u01b0u ti\u00ean h\u01a1n so v\u1edbi t\u00ednh nh\u1ea5t qu\u00e1n khi ghi. C\u00e1c c\u1ed9t \u0111\u00e3 \u0111\u01b0\u1ee3c t\u00ednh to\u00e1n tr\u01b0\u1edbc c\u00f3 th\u1ec3 gi\u1ea3m \u0111\u1ed9 ph\u1ee9c t\u1ea1p c\u1ee7a ph\u00e9p n\u1ed1i.<\/li>\n
            • C\u00e1c b\u1ea3n ch\u1ee5p l\u1ecbch s\u1eed:<\/strong> N\u1ebfu b\u1ea1n c\u1ea7n bi\u1ebft \u0111\u1ecba ch\u1ec9 c\u1ee7a kh\u00e1ch h\u00e0ng l\u00e0 g\u00ec v\u00e0o th\u1eddi \u0111i\u1ec3m \u0111\u1eb7t h\u00e0ng, b\u1ea1n kh\u00f4ng th\u1ec3 d\u1ef1a v\u00e0o \u0111\u1ecba ch\u1ec9 hi\u1ec7n t\u1ea1i trong b\u1ea3ng Kh\u00e1ch h\u00e0ng. B\u1ea1n ph\u1ea3i l\u01b0u \u0111\u1ecba ch\u1ec9 \u0111\u00f3 trong b\u1ea3ng \u0110\u01a1n h\u00e0ng.<\/li>\n
            • T\u1ed1i \u01b0u hi\u1ec7u su\u1ea5t:<\/strong> N\u1ebfu c\u00e1c truy v\u1ea5n li\u00ean t\u1ee5c ch\u1eadm do c\u00e1c ph\u00e9p n\u1ed1i, vi\u1ec7c th\u00eam m\u1ed9t c\u1ed9t tr\u00f9ng l\u1eb7p \u0111\u01b0\u1ee3c c\u1eadp nh\u1eadt th\u00f4ng qua trigger ho\u1eb7c logic \u1ee9ng d\u1ee5ng c\u00f3 th\u1ec3 l\u00e0 c\u1ea7n thi\u1ebft.<\/li>\n<\/ul>\n

              \u0110i\u1ec1u then ch\u1ed1t l\u00e0 s\u1ef1 ch\u1ee7 \u00fd. \u0110\u1eebng ch\u1ea5p nh\u1eadn s\u1ef1 tr\u00f9ng l\u1eb7p nh\u01b0 m\u1ed9t m\u1eb7c \u0111\u1ecbnh. Ch\u1ec9 ch\u1ea5p nh\u1eadn n\u00f3 khi c\u00f3 l\u1ee3i \u00edch hi\u1ec7u su\u1ea5t \u0111o l\u01b0\u1eddng \u0111\u01b0\u1ee3c, v\u01b0\u1ee3t tr\u1ed9i h\u01a1n chi ph\u00ed b\u1ea3o tr\u00ec.<\/p>\n

              \ud83d\udd04 Xem x\u00e9t v\u00e0 duy tr\u00ec l\u01b0\u1ee3c \u0111\u1ed3 c\u1ee7a b\u1ea1n<\/h2>\n

              Chu\u1ea9n h\u00f3a kh\u00f4ng ph\u1ea3i l\u00e0 m\u1ed9t c\u00f4ng vi\u1ec7c m\u1ed9t l\u1ea7n. Y\u00eau c\u1ea7u kinh doanh thay \u0111\u1ed5i, v\u00e0 d\u1eef li\u1ec7u ng\u00e0y c\u00e0ng t\u0103ng. M\u1ed9t l\u01b0\u1ee3c \u0111\u1ed3 \u0111\u00e3 \u0111\u01b0\u1ee3c chu\u1ea9n h\u00f3a c\u00e1ch \u0111\u00e2y n\u0103m n\u0103m c\u00f3 th\u1ec3 c\u1ea7n \u0111i\u1ec1u ch\u1ec9nh ng\u00e0y nay.<\/p>\n

              Ki\u1ec3m to\u00e1n \u0111\u1ecbnh k\u1ef3<\/h3>\n

              L\u00ean l\u1ecbch ki\u1ec3m tra \u0111\u1ecbnh k\u1ef3 s\u01a1 \u0111\u1ed3 ERD c\u1ee7a b\u1ea1n. T\u00ecm ki\u1ebfm c\u00e1c m\u1eabu d\u1eef li\u1ec7u b\u1ecb l\u1eb7p l\u1ea1i. N\u1ebfu b\u1ea1n ph\u00e1t hi\u1ec7n c\u00f9ng m\u1ed9t chu\u1ed7i v\u0103n b\u1ea3n xu\u1ea5t hi\u1ec7n trong nhi\u1ec1u b\u1ea3ng, h\u00e3y \u0111i\u1ec1u tra l\u00fd do. \u0110i\u1ec1u n\u00e0y c\u00f3 th\u1ec3 l\u00e0 d\u1ea5u hi\u1ec7u c\u1ee7a l\u1ed7i thi\u1ebft k\u1ebf ho\u1eb7c l\u1ef1a ch\u1ecdn kh\u00f4ng chu\u1ea9n h\u00f3a c\u00f3 ch\u1ee7 \u00fd, c\u1ea7n \u0111\u01b0\u1ee3c ghi ch\u00e9p l\u1ea1i.<\/p>\n

              Ki\u1ec3m so\u00e1t phi\u00ean b\u1ea3n cho c\u00e1c m\u00f4 h\u00ecnh d\u1eef li\u1ec7u<\/h3>\n

              Xem s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 (ERD) c\u1ee7a b\u1ea1n nh\u01b0 m\u00e3 ngu\u1ed3n. S\u1eed d\u1ee5ng h\u1ec7 th\u1ed1ng ki\u1ec3m so\u00e1t phi\u00ean b\u1ea3n \u0111\u1ec3 theo d\u00f5i c\u00e1c thay \u0111\u1ed5i. \u0110i\u1ec1u n\u00e0y cho ph\u00e9p b\u1ea1n ho\u00e0n nguy\u00ean n\u1ebfu m\u1ed9t thay \u0111\u1ed5i g\u00e2y ra s\u1ef1 tr\u00f9ng l\u1eb7p ho\u1eb7c l\u00e0m h\u1ecfng c\u00e1c m\u1ed1i quan h\u1ec7. Ghi ch\u00e9p l\u00fd do cho m\u1ecdi thay \u0111\u1ed5i c\u1ea5u tr\u00fac l\u1edbn.<\/p>\n

              \u0110\u00e0o t\u1ea1o \u0111\u1ed9i ng\u0169<\/h3>\n

              \u0110\u1ea3m b\u1ea3o r\u1eb1ng m\u1ecdi ng\u01b0\u1eddi tham gia nh\u1eadp d\u1eef li\u1ec7u ho\u1eb7c ph\u00e1t tri\u1ec3n \u1ee9ng d\u1ee5ng \u0111\u1ec1u hi\u1ec3u r\u00f5 c\u00e1c quy t\u1eafc chu\u1ea9n h\u00f3a. N\u1ebfu c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n b\u1ecf qua l\u01b0\u1ee3c \u0111\u1ed3 \u0111\u1ec3 ch\u00e8n d\u1eef li\u1ec7u tr\u1ef1c ti\u1ebfp, h\u1ecd c\u00f3 th\u1ec3 t\u00e1i t\u1ea1o l\u1ea1i s\u1ef1 tr\u00f9ng l\u1eb7p th\u00f4ng qua logic \u1ee9ng d\u1ee5ng. T\u00e0i li\u1ec7u r\u00f5 r\u00e0ng v\u1ec1 l\u00fd do t\u1ea1i sao l\u01b0\u1ee3c \u0111\u1ed3 \u0111\u01b0\u1ee3c c\u1ea5u tr\u00fac theo c\u00e1ch n\u00e0y l\u00e0 \u0111i\u1ec1u c\u1ea7n thi\u1ebft.<\/p>\n

              \ud83d\udcdd T\u00f3m t\u1eaft c\u00e1c th\u1ef1c h\u00e0nh t\u1ed1t nh\u1ea5t<\/h2>\n

              \u0110\u1ec3 duy tr\u00ec ti\u00eau chu\u1ea9n cao v\u1ec1 ch\u1ea5t l\u01b0\u1ee3ng d\u1eef li\u1ec7u v\u00e0 hi\u1ec7u qu\u1ea3 l\u01b0u tr\u1eef, tu\u00e2n theo danh s\u00e1ch ki\u1ec3m tra sau trong qu\u00e1 tr\u00ecnh thi\u1ebft k\u1ebf c\u1ee7a b\u1ea1n.<\/p>\n

                \n
              • T\u00ednh nguy\u00ean t\u1eed:<\/strong> \u0110\u1ea3m b\u1ea3o m\u1ed7i c\u1ed9t ch\u1ec9 ch\u1ee9a m\u1ed9t gi\u00e1 tr\u1ecb duy nh\u1ea5t (1NF).<\/li>\n
              • S\u1ef1 ph\u1ee5 thu\u1ed9c \u0111\u1ea7y \u0111\u1ee7:<\/strong> \u0110\u1ea3m b\u1ea3o c\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng kh\u00f3a ph\u1ee5 thu\u1ed9c v\u00e0o to\u00e0n b\u1ed9 kh\u00f3a ch\u00ednh (2NF).<\/li>\n
              • Kh\u00f4ng c\u00f3 ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u:<\/strong> \u0110\u1ea3m b\u1ea3o c\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng kh\u00f3a kh\u00f4ng ph\u1ee5 thu\u1ed9c v\u00e0o c\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng kh\u00f3a kh\u00e1c (3NF).<\/li>\n
              • Kh\u00f3a nh\u1ea5t qu\u00e1n:<\/strong> \u0110\u1ea3m b\u1ea3o m\u1ecdi y\u1ebfu t\u1ed1 x\u00e1c \u0111\u1ecbnh \u0111\u1ec1u l\u00e0 kh\u00f3a kh\u1ea3 d\u1ee5ng (BCNF).<\/li>\n
              • Ghi ch\u00e9p c\u00e1c quy\u1ebft \u0111\u1ecbnh:<\/strong> Ghi l\u1ea1i l\u00fd do t\u1ea1i sao c\u00e1c s\u1ef1 tr\u00f9ng l\u1eb7p c\u1ee5 th\u1ec3 \u0111\u00e3 \u0111\u01b0\u1ee3c \u0111\u01b0a v\u00e0o.<\/li>\n
              • Theo d\u00f5i s\u1ef1 ph\u00e1t tri\u1ec3n:<\/strong> Quan s\u00e1t c\u00e1c m\u1eabu d\u1eef li\u1ec7u b\u1ecb l\u1eb7p l\u1ea1i khi c\u01a1 s\u1edf d\u1eef li\u1ec7u m\u1edf r\u1ed9ng.<\/li>\n<\/ul>\n

                B\u1eb1ng c\u00e1ch tu\u00e2n theo c\u00e1c nguy\u00ean t\u1eafc n\u00e0y, b\u1ea1n t\u1ea1o ra m\u1ed9t h\u1ec7 th\u1ed1ng c\u00f3 kh\u1ea3 n\u0103ng ch\u1ed1ng ch\u1ecbu v\u1edbi s\u1ef1 thay \u0111\u1ed5i. D\u1eef li\u1ec7u v\u1eabn \u0111\u01b0\u1ee3c gi\u1eef s\u1ea1ch s\u1ebd, v\u00e0 logic v\u1eabn h\u1ee3p l\u00fd. Kh\u00f4ng tr\u00f9ng l\u1eb7p kh\u00f4ng ch\u1ec9 nh\u1eb1m ti\u1ebft ki\u1ec7m dung l\u01b0\u1ee3ng \u1ed5 \u0111\u0129a; \u0111\u00f3 l\u00e0 x\u00e2y d\u1ef1ng n\u1ec1n t\u1ea3ng n\u01a1i s\u1ef1 th\u1eadt c\u1ee7a d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c b\u1ea3o to\u00e0n.<\/p>\n

                \ud83d\ude80 Nh\u1eefng suy ngh\u0129 cu\u1ed1i c\u00f9ng v\u1ec1 t\u00ednh to\u00e0n v\u1eb9n c\u1ea5u tr\u00fac<\/h2>\n

                H\u00e0nh tr\u00ecnh h\u01b0\u1edbng t\u1edbi l\u01b0u tr\u1eef kh\u00f4ng tr\u00f9ng l\u1eb7p l\u00e0 m\u1ed9t kho\u1ea3n \u0111\u1ea7u t\u01b0 v\u00e0o s\u1ef1 b\u1ec1n v\u1eefng c\u1ee7a ki\u1ebfn tr\u00fac d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n. D\u00f9 n\u00f3 \u0111\u00f2i h\u1ecfi s\u1ef1 k\u1ef7 lu\u1eadt trong giai \u0111o\u1ea1n thi\u1ebft k\u1ebf, nh\u01b0ng l\u1ee3i \u00edch mang l\u1ea1i l\u00e0 gi\u1ea3m l\u1ed7i, chi ph\u00ed b\u1ea3o tr\u00ec th\u1ea5p h\u01a1n v\u00e0 ni\u1ec1m tin cao h\u01a1n v\u00e0o h\u1ec7 th\u1ed1ng th\u00f4ng tin.<\/p>\n

                Khi b\u1ea1n nh\u00ecn v\u00e0o s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3, h\u00e3y xem n\u00f3 kh\u00f4ng ch\u1ec9 l\u00e0 m\u1ed9t t\u1eadp h\u1ee3p c\u00e1c h\u00ecnh h\u1ed9p v\u00e0 \u0111\u01b0\u1eddng k\u1ebb, m\u00e0 l\u00e0 b\u1ea3n \u0111\u1ed3 c\u1ee7a s\u1ef1 th\u1eadt. M\u1ed7i \u0111\u01b0\u1eddng k\u1ebb \u0111\u1ea1i di\u1ec7n cho m\u1ed9t m\u1ed1i quan h\u1ec7 c\u1ea7n thi\u1ebft. M\u1ed7i h\u00ecnh h\u1ed9p \u0111\u1ea1i di\u1ec7n cho m\u1ed9t s\u1ef1 ki\u1ec7n ri\u00eang bi\u1ec7t. B\u1eb1ng c\u00e1ch chu\u1ea9n h\u00f3a hi\u1ec7u qu\u1ea3, b\u1ea1n \u0111\u1ea3m b\u1ea3o b\u1ea3n \u0111\u1ed3 n\u00e0y v\u1eabn ch\u00ednh x\u00e1c, ngay c\u1ea3 khi \u0111\u1ecba h\u00ecnh kinh doanh c\u1ee7a b\u1ea1n thay \u0111\u1ed5i.<\/p>\n

                T\u1eadp trung v\u00e0o logic, ch\u1ee9 kh\u00f4ng ch\u1ec9 l\u00e0 l\u01b0u tr\u1eef. \u0110\u1ec3 c\u1ea5u tr\u00fac ph\u1ee5c v\u1ee5 d\u1eef li\u1ec7u, ch\u1ee9 kh\u00f4ng ph\u1ea3i ng\u01b0\u1ee3c l\u1ea1i. V\u1edbi s\u1ef1 hi\u1ec3u r\u00f5 v\u1ec1 c\u00e1c chi\u1ebfn l\u01b0\u1ee3c chu\u1ea9n h\u00f3a, b\u1ea1n s\u1ebd s\u1eb5n s\u00e0ng x\u00e2y d\u1ef1ng c\u00e1c h\u1ec7 th\u1ed1ng v\u01b0\u1ee3t qua th\u1eed th\u00e1ch c\u1ee7a th\u1eddi gian v\u00e0 kh\u1ed1i l\u01b0\u1ee3ng d\u1eef li\u1ec7u.<\/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 th\u00f4ng tin \u0111\u00e1ng tin c\u1eady n\u00e0o. \u1ede trung t\u00e2m c\u1ee7a thi\u1ebft k\u1ebf n\u00e0y…<\/p>\n","protected":false},"author":1,"featured_media":1705,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_yoast_wpseo_title":"Chi\u1ebfn l\u01b0\u1ee3c chu\u1ea9n h\u00f3a s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 cho l\u01b0u tr\u1eef kh\u00f4ng tr\u00f9ng l\u1eb7p","_yoast_wpseo_metadesc":"H\u1ecdc c\u00e1c chi\u1ebfn l\u01b0\u1ee3c chu\u1ea9n h\u00f3a s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 cho l\u01b0u tr\u1eef kh\u00f4ng tr\u00f9ng l\u1eb7p. 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