{"id":1641,"date":"2026-04-07T22:58:20","date_gmt":"2026-04-07T22:58:20","guid":{"rendered":"https:\/\/www.viz-note.com\/vi\/common-erd-mistakes-data-integrity-violations\/"},"modified":"2026-04-07T22:58:20","modified_gmt":"2026-04-07T22:58:20","slug":"common-erd-mistakes-data-integrity-violations","status":"publish","type":"post","link":"https:\/\/www.viz-note.com\/vi\/common-erd-mistakes-data-integrity-violations\/","title":{"rendered":"Nh\u1eefng sai l\u1ea7m ph\u1ed5 bi\u1ebfn trong m\u00f4 h\u00ecnh h\u00f3a s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 d\u1eabn \u0111\u1ebfn vi ph\u1ea1m t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u"},"content":{"rendered":"

Thi\u1ebft k\u1ebf m\u1ed9t c\u1ea5u tr\u00fac c\u01a1 s\u1edf d\u1eef li\u1ec7u m\u1ea1nh m\u1ebd b\u1eaft \u0111\u1ea7u b\u1eb1ng m\u1ed9t k\u1ebf ho\u1ea1ch ch\u00ednh x\u00e1c. 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 d\u1eef li\u1ec7u s\u1ebd \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef, li\u00ean k\u1ebft v\u00e0 truy c\u1eadp. Tuy nhi\u00ean, ngay c\u1ea3 nh\u1eefng ki\u1ebfn tr\u00fac s\u01b0 c\u00f3 kinh nghi\u1ec7m c\u0169ng c\u00f3 th\u1ec3 \u0111\u01b0a v\u00e0o nh\u1eefng l\u1ed7i tinh vi trong giai \u0111o\u1ea1n m\u00f4 h\u00ecnh h\u00f3a. Nh\u1eefng l\u1ed7i n\u00e0y th\u01b0\u1eddng th\u1ec3 hi\u1ec7n r\u00f5 h\u01a1n sau n\u00e0y d\u01b0\u1edbi d\u1ea1ng vi ph\u1ea1m nghi\u00eam tr\u1ecdng v\u1ec1 t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u. Khi t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u th\u1ea5t b\u1ea1i, \u0111\u1ed9 tin c\u1eady c\u1ee7a to\u00e0n b\u1ed9 \u1ee9ng d\u1ee5ng s\u1ebd b\u1ecb \u1ea3nh h\u01b0\u1edfng. \ud83d\uded1<\/p>\n

T\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u \u0111\u1ec1 c\u1eadp \u0111\u1ebfn \u0111\u1ed9 ch\u00ednh x\u00e1c, t\u00ednh nh\u1ea5t qu\u00e1n v\u00e0 \u0111\u1ed9 tin c\u1eady c\u1ee7a d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef trong c\u01a1 s\u1edf d\u1eef li\u1ec7u. N\u00f3 \u0111\u1ea3m b\u1ea3o r\u1eb1ng th\u00f4ng tin lu\u00f4n \u0111\u01b0\u1ee3c gi\u1eef nguy\u00ean v\u00e0 h\u1ee3p l\u1ec7 trong su\u1ed1t v\u00f2ng \u0111\u1eddi c\u1ee7a n\u00f3. M\u1ed9t s\u01a1 \u0111\u1ed3 ERD \u0111\u01b0\u1ee3c x\u00e2y d\u1ef1ng t\u1ed1t s\u1ebd ng\u0103n ch\u1eb7n c\u00e1c hi\u1ec7n t\u01b0\u1ee3ng b\u1ea5t th\u01b0\u1eddng nh\u01b0 b\u1ea3n ghi b\u1ecb b\u1ecf r\u01a1i, c\u00e1c b\u1ea3n ghi tr\u00f9ng l\u1eb7p v\u00e0 c\u00e1c gi\u00e1 tr\u1ecb kh\u00f4ng nh\u1ea5t qu\u00e1n. H\u01b0\u1edbng d\u1eabn n\u00e0y s\u1ebd ph\u00e2n t\u00edch nh\u1eefng sai s\u00f3t m\u00f4 h\u00ecnh h\u00f3a ph\u1ed5 bi\u1ebfn nh\u1ea5t l\u00e0m suy y\u1ebfu c\u00e1c bi\u1ec7n ph\u00e1p b\u1ea3o v\u1ec7 n\u00e0y. Ch\u00fang ta s\u1ebd kh\u00e1m ph\u00e1 c\u00e1c h\u1ec7 qu\u1ea3 k\u1ef9 thu\u1eadt c\u1ee7a t\u1eebng sai l\u1ea7m v\u00e0 n\u00eau r\u00f5 c\u00e1ch kh\u1eafc ph\u1ee5c ch\u00fang. \ud83d\udd0d<\/p>\n

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\"Line<\/figure>\n<\/div>\n

Hi\u1ec3u r\u00f5 v\u1ec1 t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u trong thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u \ud83c\udfd7\ufe0f<\/h2>\n

Tr\u01b0\u1edbc khi \u0111i v\u00e0o c\u00e1c l\u1ed7i c\u1ee5 th\u1ec3, \u0111i\u1ec1u quan tr\u1ecdng l\u00e0 ph\u1ea3i \u0111\u1ecbnh ngh\u0129a r\u00f5 \u00fd ngh\u0129a c\u1ee7a t\u00ednh to\u00e0n v\u1eb9n trong b\u1ed1i c\u1ea3nh n\u00e0y. T\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u kh\u00f4ng ch\u1ec9 \u0111\u01a1n thu\u1ea7n l\u00e0 ng\u0103n ch\u1eb7n s\u1ef1 s\u1eadp h\u1ec7 th\u1ed1ng; n\u00f3 l\u00e0 vi\u1ec7c duy tr\u00ec c\u00e1c quy t\u1eafc logic. C\u00f3 b\u1ed1n lo\u1ea1i t\u00ednh to\u00e0n v\u1eb9n ch\u00ednh m\u00e0 s\u01a1 \u0111\u1ed3 ERD ph\u1ea3i h\u1ed7 tr\u1ee3:<\/p>\n

    \n
  • T\u00ednh to\u00e0n v\u1eb9n th\u1ef1c th\u1ec3:<\/strong>\u0110\u1ea3m b\u1ea3o m\u1ecdi b\u1ea3ng \u0111\u1ec1u c\u00f3 kh\u00f3a ch\u00ednh duy nh\u1ea5t. Kh\u00f4ng \u0111\u01b0\u1ee3c ph\u00e9p c\u00f3 gi\u00e1 tr\u1ecb null trong c\u1ed9t kh\u00f3a ch\u00ednh.<\/li>\n
  • T\u00ednh to\u00e0n v\u1eb9n tham chi\u1ebfu:<\/strong>Duy tr\u00ec s\u1ef1 nh\u1ea5t qu\u00e1n gi\u1eefa c\u00e1c b\u1ea3ng. Kh\u00f3a ngo\u1ea1i ph\u1ea3i kh\u1edbp v\u1edbi kh\u00f3a ch\u00ednh trong b\u1ea3ng cha ho\u1eb7c c\u00f3 th\u1ec3 l\u00e0 null.<\/li>\n
  • T\u00ednh to\u00e0n v\u1eb9n mi\u1ec1n:<\/strong>X\u00e1c \u0111\u1ecbnh c\u00e1c gi\u00e1 tr\u1ecb h\u1ee3p l\u1ec7 cho m\u1ed9t c\u1ed9t c\u1ee5 th\u1ec3, ch\u1eb3ng h\u1ea1n nh\u01b0 ki\u1ec3u d\u1eef li\u1ec7u, \u0111\u1ed9 d\u00e0i v\u00e0 c\u00e1c r\u00e0ng bu\u1ed9c ph\u1ea1m vi.<\/li>\n
  • T\u00ednh to\u00e0n v\u1eb9n do ng\u01b0\u1eddi d\u00f9ng \u0111\u1ecbnh ngh\u0129a:<\/strong>C\u00e1c quy t\u1eafc kinh doanh c\u1ee5 th\u1ec3 c\u1ee7a t\u1ed5 ch\u1ee9c, ch\u1eb3ng h\u1ea1n nh\u01b0 gi\u1edbi h\u1ea1n \u0111\u1ed9 tu\u1ed5i ho\u1eb7c m\u00e3 tr\u1ea1ng th\u00e1i.<\/li>\n<\/ul>\n

    Khi s\u01a1 \u0111\u1ed3 ERD kh\u00f4ng ph\u1ea3n \u00e1nh \u0111\u00fang nh\u1eefng quy t\u1eafc n\u00e0y, b\u1ed9 \u0111\u1ed9ng c\u01a1 c\u01a1 s\u1edf d\u1eef li\u1ec7u kh\u00f4ng th\u1ec3 t\u1ef1 \u0111\u1ed9ng th\u1ef1c thi ch\u00fang. \u0110i\u1ec1u n\u00e0y bu\u1ed9c c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n ph\u1ea3i vi\u1ebft m\u00e3 c\u1ea5p \u1ee9ng d\u1ee5ng \u0111\u1ec3 ki\u1ec3m tra l\u1ed7i, \u0111i\u1ec1u n\u00e0y th\u01b0\u1eddng ch\u1eadm h\u01a1n v\u00e0 \u00edt \u0111\u00e1ng tin c\u1eady h\u01a1n. M\u1ed9t s\u01a1 \u0111\u1ed3 \u0111\u00fang \u0111\u1eafn \u0111\u00f3ng vai tr\u00f2 nh\u01b0 m\u1ed9t h\u1ee3p \u0111\u1ed3ng gi\u1eefa c\u1ea5u tr\u00fac d\u1eef li\u1ec7u v\u00e0 logic \u1ee9ng d\u1ee5ng. \ud83e\udd1d<\/p>\n

    Sai l\u1ea7m 1: C\u00e1c m\u1ed1i quan h\u1ec7 b\u1eadc thang m\u01a1 h\u1ed3 \ud83d\udd04<\/h2>\n

    M\u1ed9t trong nh\u1eefng sai l\u1ea7m ph\u1ed5 bi\u1ebfn nh\u1ea5t l\u00e0 x\u00e1c \u0111\u1ecbnh c\u00e1c m\u1ed1i quan h\u1ec7 m\u00e0 kh\u00f4ng r\u00f5 r\u00e0ng v\u1ec1 b\u1eadc thang. B\u1eadc thang x\u00e1c \u0111\u1ecbnh m\u1ed1i quan h\u1ec7 s\u1ed1 l\u01b0\u1ee3ng gi\u1eefa c\u00e1c th\u1ef1c th\u1ec3 trong m\u1ed9t m\u1ed1i quan h\u1ec7. N\u00f3 x\u00e1c \u0111\u1ecbnh xem m\u1ed9t th\u1ec3 hi\u1ec7n c\u1ee7a th\u1ef1c th\u1ec3 c\u00f3 li\u00ean k\u1ebft v\u1edbi m\u1ed9t, nhi\u1ec1u hay kh\u00f4ng c\u00f3 th\u1ec3 hi\u1ec7n n\u00e0o c\u1ee7a th\u1ef1c th\u1ec3 kh\u00e1c hay kh\u00f4ng.<\/p>\n

    V\u1ea5n \u0111\u1ec1<\/h3>\n

    C\u00e1c nh\u00e0 m\u00f4 h\u00ecnh th\u01b0\u1eddng v\u1ebd m\u1ed9t \u0111\u01b0\u1eddng n\u1ed1i gi\u1eefa hai th\u1ef1c th\u1ec3 m\u00e0 kh\u00f4ng x\u00e1c \u0111\u1ecbnh h\u01b0\u1edbng hay s\u1ed1 l\u01b0\u1ee3ng. V\u00ed d\u1ee5, li\u00ean k\u1ebft m\u1ed9tKh\u00e1ch h\u00e0ng<\/em>v\u1edbi m\u1ed9t\u0110\u01a1n h\u00e0ng<\/em>m\u00e0 kh\u00f4ng n\u00eau r\u00f5 kh\u00e1ch h\u00e0ng c\u00f3 th\u1ec3 c\u00f3 nhi\u1ec1u \u0111\u01a1n h\u00e0ng hay kh\u00f4ng. N\u1ebfu m\u1ed1i quan h\u1ec7 \u0111\u01b0\u1ee3c x\u1eed l\u00fd nh\u01b0 m\u1ed9t-m\u1ed9t (1:1) trong khi th\u1ef1c t\u1ebf ph\u1ea3i l\u00e0 m\u1ed9t-nhi\u1ec1u (1:N), d\u1eef li\u1ec7u s\u1ebd b\u1ecb gi\u1edbi h\u1ea1n. Ng\u01b0\u1ee3c l\u1ea1i, x\u1eed l\u00fd m\u1ed1i quan h\u1ec7 1:1 nh\u01b0 1:N s\u1ebd d\u1eabn \u0111\u1ebfn s\u1ef1 d\u01b0 th\u1eeba.<\/p>\n

    H\u1eadu qu\u1ea3<\/h3>\n
      \n
    • D\u01b0 th\u1eeba d\u1eef li\u1ec7u:<\/strong>N\u1ebfu m\u1ed1i quan h\u1ec7 1:1 \u0111\u01b0\u1ee3c m\u00f4 h\u00ecnh h\u00f3a th\u00e0nh 1:N, b\u1ea1n c\u00f3 th\u1ec3 s\u1ebd l\u01b0u th\u00f4ng tin kh\u00e1ch h\u00e0ng trong nhi\u1ec1u b\u1ea3n ghi \u0111\u01a1n h\u00e0ng kh\u00e1c nhau.<\/li>\n
    • Hi\u1ec7n t\u01b0\u1ee3ng b\u1ea5t th\u01b0\u1eddng khi c\u1eadp nh\u1eadt:<\/strong>Vi\u1ec7c thay \u0111\u1ed5i \u0111\u1ecba ch\u1ec9 kh\u00e1ch h\u00e0ng trong m\u1ed9t b\u1ea3n ghi c\u00f3 th\u1ec3 kh\u00f4ng \u0111\u01b0\u1ee3c c\u1eadp nh\u1eadt trong b\u1ea3n ghi li\u00ean quan kh\u00e1c.<\/li>\n
    • Suy gi\u1ea3m hi\u1ec7u su\u1ea5t:<\/strong>C\u00e1c thao t\u00e1c n\u1ed1i (join) tr\u1edf n\u00ean k\u00e9m hi\u1ec7u qu\u1ea3 khi b\u1eadc thang kh\u00f4ng \u0111\u01b0\u1ee3c t\u1ed1i \u01b0u.<\/li>\n<\/ul>\n

      Gi\u1ea3i ph\u00e1p<\/h3>\n

      Lu\u00f4n x\u00e1c \u0111\u1ecbnh m\u1ed1i quan h\u1ec7 m\u1ed9t c\u00e1ch r\u00f5 r\u00e0ng. S\u1eed d\u1ee5ng k\u00fd hi\u1ec7u ch\u00e2n chim \u0111\u1ec3 ch\u1ec9 ph\u00eda “nhi\u1ec1u”. \u0110\u1ea3m b\u1ea3o r\u1eb1ng m\u1ed7i v\u1ecb tr\u00ed kh\u00f3a ngo\u1ea1i \u0111\u1ec1u ph\u00f9 h\u1ee3p v\u1edbi c\u1ea5p \u0111\u1ed9 quan h\u1ec7 mong mu\u1ed1n. Kh\u00f3a ngo\u1ea1i ph\u1ea3i n\u1eb1m \u1edf ph\u00eda “nhi\u1ec1u” trong m\u1ed1i quan h\u1ec7 m\u1ed9t-\u0111a. \u0110\u1ed1i v\u1edbi c\u00e1c m\u1ed1i quan h\u1ec7 \u0111a-\u0111a, b\u1ea3ng li\u00ean k\u1ebft l\u00e0 b\u1eaft bu\u1ed9c. B\u1ea3ng n\u00e0y chia m\u1ed1i quan h\u1ec7 th\u00e0nh hai m\u1ed1i quan h\u1ec7 m\u1ed9t-\u0111a. \ud83d\udcca<\/p>\n

      L\u1ed7i 2: B\u1ecf qua c\u00e1c r\u00e0ng bu\u1ed9c to\u00e0n v\u1eb9n tham chi\u1ebfu \ud83d\udeab<\/h2>\n

      To\u00e0n v\u1eb9n tham chi\u1ebfu \u0111\u1ea3m b\u1ea3o c\u00e1c m\u1ed1i quan h\u1ec7 gi\u1eefa c\u00e1c b\u1ea3ng lu\u00f4n nh\u1ea5t qu\u00e1n. N\u00f3 ng\u0103n ch\u1eb7n c\u00e1c b\u1ea3n ghi “m\u1ed3 c\u00f4i”, t\u1ee9c l\u00e0 c\u00e1c h\u00e0ng trong b\u1ea3ng con tham chi\u1ebfu \u0111\u1ebfn m\u1ed9t h\u00e0ng kh\u00f4ng t\u1ed3n t\u1ea1i trong b\u1ea3ng cha.<\/p>\n

      V\u1ea5n \u0111\u1ec1<\/h3>\n

      Trong qu\u00e1 tr\u00ecnh m\u00f4 h\u00ecnh h\u00f3a, c\u00e1c ki\u1ebfn tr\u00fac s\u01b0 \u0111\u00f4i khi qu\u00ean \u0111\u1ecbnh ngh\u0129a r\u00e0ng bu\u1ed9c kh\u00f3a ngo\u1ea1i trong s\u01a1 \u0111\u1ed3. H\u1ecd c\u00f3 th\u1ec3 x\u00e1c \u0111\u1ecbnh m\u1ed1i quan h\u1ec7 v\u1ec1 m\u1eb7t tr\u1ef1c quan nh\u01b0ng b\u1ecf qua logic r\u00e0ng bu\u1ed9c. \u0110i\u1ec1u n\u00e0y khi\u1ebfn c\u01a1 s\u1edf d\u1eef li\u1ec7u d\u1ec5 b\u1ecb nh\u1eadp d\u1eef li\u1ec7u kh\u00f4ng h\u1ee3p l\u1ec7. V\u00ed d\u1ee5, m\u1ed9t \u0110\u01a1n h\u00e0ng<\/em> c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c t\u1ea1o cho m\u1ed9t S\u1ea3n ph\u1ea9m<\/em> ID kh\u00f4ng t\u1ed3n t\u1ea1i trong b\u1ea3ng S\u1ea3n ph\u1ea9m<\/em> b\u1ea3ng.<\/p>\n

      H\u1eadu qu\u1ea3<\/h3>\n
        \n
      • L\u1ed7i lan truy\u1ec1n:<\/strong>X\u00f3a m\u1ed9t b\u1ea3n ghi cha c\u00f3 th\u1ec3 \u0111\u1ec3 l\u1ea1i c\u00e1c b\u1ea3n ghi con kh\u00f4ng c\u00f3 li\u00ean k\u1ebft h\u1ee3p l\u1ec7.<\/li>\n
      • L\u1ed7i truy v\u1ea5n:<\/strong>C\u00e1c truy v\u1ea5n k\u1ebft h\u1ee3p c\u00f3 th\u1ec3 tr\u1ea3 v\u1ec1 k\u1ebft qu\u1ea3 kh\u00f4ng mong \u0111\u1ee3i ho\u1eb7c th\u1ea5t b\u1ea1i ho\u00e0n to\u00e0n n\u1ebfu li\u00ean k\u1ebft b\u1ecb gi\u00e1n \u0111o\u1ea1n.<\/li>\n
      • L\u1ed7i b\u00e1o c\u00e1o:<\/strong>C\u00e1c truy v\u1ea5n t\u1ed5ng h\u1ee3p d\u1ef1a tr\u00ean c\u00e1c m\u1ed1i quan h\u1ec7 n\u00e0y s\u1ebd t\u1ea1o ra t\u1ed5ng sai l\u1ec7ch.<\/li>\n<\/ul>\n

        Gi\u1ea3i ph\u00e1p<\/h3>\n

        M\u00f4 h\u00ecnh h\u00f3a r\u00f5 r\u00e0ng c\u00e1c kh\u00f3a ngo\u1ea1i trong s\u01a1 \u0111\u1ed3 ERD. Ch\u1ec9 r\u00f5 h\u00e0nh \u0111\u1ed9ng c\u1ea7n th\u1ef1c hi\u1ec7n khi b\u1ea3n ghi cha b\u1ecb x\u00f3a ho\u1eb7c c\u1eadp nh\u1eadt. C\u00e1c h\u00e0nh \u0111\u1ed9ng ph\u1ed5 bi\u1ebfn bao g\u1ed3m:<\/p>\n

          \n
        • LAN TRUY\u1ec0N:<\/strong>T\u1ef1 \u0111\u1ed9ng x\u00f3a ho\u1eb7c c\u1eadp nh\u1eadt c\u00e1c b\u1ea3n ghi con khi b\u1ea3n ghi cha thay \u0111\u1ed5i.<\/li>\n
        • \u0110\u1eb6T L\u00c0 NULL:<\/strong>\u0110\u1eb7t kh\u00f3a ngo\u1ea1i trong b\u1ea3n ghi con th\u00e0nh null n\u1ebfu b\u1ea3n ghi cha b\u1ecb x\u00f3a.<\/li>\n
        • H\u1ea0N CH\u1ebe:<\/strong>Ng\u0103n vi\u1ec7c x\u00f3a b\u1ea3n ghi cha n\u1ebfu t\u1ed3n t\u1ea1i c\u00e1c b\u1ea3n ghi con.<\/li>\n<\/ul>\n

          Vi\u1ec7c ch\u1ecdn h\u00e0nh \u0111\u1ed9ng ph\u00f9 h\u1ee3p ph\u1ee5 thu\u1ed9c v\u00e0o logic kinh doanh. V\u00ed d\u1ee5, b\u1ea1n c\u00f3 th\u1ec3 h\u1ea1n ch\u1ebf vi\u1ec7c x\u00f3a m\u1ed9t Nh\u00e0 cung c\u1ea5p<\/em> n\u1ebfu t\u1ed3n t\u1ea1i c\u00e1c \u0111\u01a1n h\u00e0ng \u0111ang ho\u1ea1t \u0111\u1ed9ng, nh\u01b0ng cho ph\u00e9p \u0111\u1ed1i v\u1edbi c\u00e1c m\u1ee5c \u0111\u00e3 l\u01b0u tr\u1eef. \ud83d\udee1\ufe0f<\/p>\n

          L\u1ed7i 3: Th\u1ef1c hi\u1ec7n c\u00e1c th\u1ef1c h\u00e0nh chu\u1ea9n h\u00f3a k\u00e9m \ud83d\udcc9<\/h2>\n

          Chu\u1ea9n h\u00f3a l\u00e0 qu\u00e1 tr\u00ecnh t\u1ed5 ch\u1ee9c d\u1eef li\u1ec7u nh\u1eb1m gi\u1ea3m thi\u1ec3u s\u1ef1 tr\u00f9ng l\u1eb7p v\u00e0 c\u1ea3i thi\u1ec7n t\u00ednh to\u00e0n v\u1eb9n. 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. B\u1ecf qua b\u01b0\u1edbc n\u00e0y ho\u1eb7c \u00e1p d\u1ee5ng sai s\u1ebd l\u00e0 ngu\u1ed3n g\u1ed1c ch\u00ednh c\u1ee7a s\u1ef1 h\u1ecfng d\u1eef li\u1ec7u.<\/p>\n

          V\u1ea5n \u0111\u1ec1<\/h3>\n

          C\u00e1c nh\u00e0 thi\u1ebft k\u1ebf th\u01b0\u1eddng t\u1ea1o m\u1ed9t b\u1ea3ng ‘ph\u1eb3ng’ duy nh\u1ea5t \u0111\u1ec3 l\u01b0u tr\u1eef m\u1ecdi th\u1ee9. V\u00ed d\u1ee5, \u0111\u1eb7t th\u00f4ng tin kh\u00e1ch h\u00e0ng b\u00ean trong b\u1ea3ng \u0111\u01a1n h\u00e0ng. M\u1eb7c d\u00f9 \u0111i\u1ec1u n\u00e0y l\u00e0m \u0111\u01a1n gi\u1ea3n h\u00f3a c\u00e1c truy v\u1ea5n ban \u0111\u1ea7u, nh\u01b0ng n\u00f3 vi ph\u1ea1m c\u00e1c nguy\u00ean t\u1eafc chu\u1ea9n h\u00f3a. C\u1ee5 th\u1ec3, n\u00f3 vi ph\u1ea1m d\u1ea1ng chu\u1ea9n th\u1ee9 ba (3NF). N\u00f3 c\u0169ng ti\u1ec1m \u1ea9n nguy c\u01a1 vi ph\u1ea1m d\u1ea1ng chu\u1ea9n th\u1ee9 hai (2NF) n\u1ebfu t\u1ed3n t\u1ea1i c\u00e1c ph\u1ee5 thu\u1ed9c ri\u00eang ph\u1ea7n.<\/p>\n

          H\u1eadu qu\u1ea3<\/h3>\n
            \n
          • L\u1ed7i ch\u00e8n:<\/strong>B\u1ea1n kh\u00f4ng th\u1ec3 th\u00eam kh\u00e1ch h\u00e0ng m\u1edbi n\u1ebfu ch\u01b0a c\u00f3 \u0111\u01a1n h\u00e0ng n\u00e0o t\u1ed3n t\u1ea1i.<\/li>\n
          • L\u1ed7i x\u00f3a:<\/strong>Vi\u1ec7c x\u00f3a m\u1ed9t \u0111\u01a1n h\u00e0ng c\u00f3 th\u1ec3 v\u00f4 t\u00ecnh x\u00f3a b\u1ecf b\u1ea3n ghi duy nh\u1ea5t c\u1ee7a m\u1ed9t kh\u00e1ch h\u00e0ng.<\/li>\n
          • L\u1ed7i c\u1eadp nh\u1eadt:<\/strong>N\u1ebfu m\u1ed9t kh\u00e1ch h\u00e0ng thay \u0111\u1ed5i s\u1ed1 \u0111i\u1ec7n tho\u1ea1i, b\u1ea1n ph\u1ea3i c\u1eadp nh\u1eadt m\u1ecdi b\u1ea3n ghi \u0111\u01a1n h\u00e0ng li\u00ean quan \u0111\u1ebfn h\u1ecd.<\/li>\n<\/ul>\n

            Gi\u1ea3i ph\u00e1p<\/h3>\n

            Tu\u00e2n th\u1ee7 c\u00e1c quy t\u1eafc chu\u1ea9n h\u00f3a ti\u00eau chu\u1ea9n trong giai \u0111o\u1ea1n thi\u1ebft k\u1ebf:<\/p>\n

              \n
            1. D\u1ea1ng chu\u1ea9n th\u1ee9 nh\u1ea5t (1NF):<\/strong>\u0110\u1ea3m b\u1ea3o c\u00e1c gi\u00e1 tr\u1ecb nguy\u00ean t\u1eed. Kh\u00f4ng c\u00f3 nh\u00f3m l\u1eb7p l\u1ea1i hay danh s\u00e1ch trong m\u1ed9t \u00f4 duy nh\u1ea5t.<\/li>\n
            2. D\u1ea1ng chu\u1ea9n th\u1ee9 hai (2NF):<\/strong>Lo\u1ea1i b\u1ecf c\u00e1c ph\u1ee5 thu\u1ed9c ri\u00eang ph\u1ea7n. T\u1ea5t c\u1ea3 c\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng kh\u00f3a ph\u1ea3i ph\u1ee5 thu\u1ed9c v\u00e0o to\u00e0n b\u1ed9 kh\u00f3a ch\u00ednh.<\/li>\n
            3. D\u1ea1ng chu\u1ea9n th\u1ee9 ba (3NF):<\/strong>Lo\u1ea1i b\u1ecf c\u00e1c ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u. C\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng kh\u00f3a kh\u00f4ng \u0111\u01b0\u1ee3c ph\u1ee5 thu\u1ed9c v\u00e0o c\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng kh\u00f3a kh\u00e1c.<\/li>\n<\/ol>\n

              M\u1eb7c d\u00f9 chu\u1ea9n h\u00f3a l\u00e0 r\u1ea5t quan tr\u1ecdng, h\u00e3y c\u00e2n nh\u1eafc vi\u1ec7c phi chu\u1ea9n h\u00f3a ch\u1ec9 \u0111\u1ed1i v\u1edbi c\u00e1c h\u1ec7 th\u1ed1ng b\u00e1o c\u00e1o c\u00f3 t\u1ea3i \u0111\u1ecdc cao, n\u01a1i hi\u1ec7u su\u1ea5t v\u01b0\u1ee3t tr\u1ed9i h\u01a1n r\u1ee7i ro v\u1ec1 t\u00ednh to\u00e0n v\u1eb9n. Lu\u00f4n ghi ch\u00fa r\u00f5 r\u00e0ng c\u00e1c tr\u01b0\u1eddng h\u1ee3p ngo\u1ea1i l\u1ec7 n\u00e0y trong m\u00f4 h\u00ecnh. \ud83d\udcdd<\/p>\n

              L\u1ed7i 4: B\u1ecf qua mi\u1ec1n thu\u1ed9c t\u00ednh v\u00e0 ki\u1ec3u d\u1eef li\u1ec7u \ud83d\udccf<\/h2>\n

              M\u1ed7i c\u1ed9t trong m\u1ed9t b\u1ea3ng \u0111\u1ec1u c\u00f3 m\u1ed9t mi\u1ec1n, t\u1ee9c l\u00e0 t\u1eadp h\u1ee3p c\u00e1c gi\u00e1 tr\u1ecb \u0111\u01b0\u1ee3c ph\u00e9p. \u0110i\u1ec1u n\u00e0y bao g\u1ed3m ki\u1ec3u d\u1eef li\u1ec7u (s\u1ed1 nguy\u00ean, chu\u1ed7i, ng\u00e0y th\u00e1ng) v\u00e0 c\u00e1c r\u00e0ng bu\u1ed9c c\u1ee5 th\u1ec3 (\u0111\u1ed9 d\u00e0i, \u0111\u1ed9 ch\u00ednh x\u00e1c, ph\u1ea1m vi).<\/p>\n

              V\u1ea5n \u0111\u1ec1<\/h3>\n

              C\u00e1c s\u01a1 \u0111\u1ed3 ERD th\u01b0\u1eddng th\u1ec3 hi\u1ec7n c\u00e1c thu\u1ed9c t\u00ednh m\u1ed9t c\u00e1ch chung chung. M\u1ed9t tr\u01b0\u1eddng c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c g\u00e1n nh\u00e3n l\u00e0 \u201cNg\u00e0y\u201d m\u00e0 kh\u00f4ng x\u00e1c \u0111\u1ecbnh c\u00f3 bao g\u1ed3m th\u1eddi gian hay kh\u00f4ng. Tr\u01b0\u1eddng \u201cGi\u00e1\u201d c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c m\u00f4 h\u00ecnh h\u00f3a b\u1eb1ng ki\u1ec3u chu\u1ed7i thay v\u00ec ki\u1ec3u s\u1ed1 th\u1eadp ph\u00e2n. S\u1ef1 m\u01a1 h\u1ed3 n\u00e0y d\u1eabn \u0111\u1ebfn vi\u1ec7c nh\u1eadp d\u1eef li\u1ec7u kh\u00f4ng nh\u1ea5t qu\u00e1n. Ng\u01b0\u1eddi d\u00f9ng c\u00f3 th\u1ec3 g\u00f5 \u201c100.00\u201d \u1edf m\u1ed9t n\u01a1i v\u00e0 \u201c100\u201d \u1edf n\u01a1i kh\u00e1c, g\u00e2y ra l\u1ed7i s\u1eafp x\u1ebfp v\u00e0 t\u00ednh to\u00e1n.<\/p>\n

              H\u1eadu qu\u1ea3<\/h3>\n
                \n
              • L\u1ed7i t\u00ednh to\u00e1n:<\/strong>X\u1eed l\u00fd s\u1ed1 nh\u01b0 v\u0103n b\u1ea3n s\u1ebd ng\u0103n c\u1ea3n c\u00e1c thao t\u00e1c to\u00e1n h\u1ecdc.<\/li>\n
              • L\u00e3ng ph\u00ed l\u01b0u tr\u1eef:<\/strong>S\u1eed d\u1ee5ng ki\u1ec3u chu\u1ed7i chung cho ng\u00e0y th\u00e1ng ti\u00eau t\u1ed1n nhi\u1ec1u kh\u00f4ng gian h\u01a1n so v\u1edbi ki\u1ec3u ng\u00e0y th\u00e1ng b\u1ea3n \u0111\u1ecba.<\/li>\n
              • Kho\u1ea3ng tr\u1ed1ng ki\u1ec3m tra:<\/strong>C\u01a1 s\u1edf d\u1eef li\u1ec7u kh\u00f4ng th\u1ec3 \u0111\u1ea3m b\u1ea3o r\u1eb1ng m\u1ed9t \u201cGi\u00e1\u201d ph\u1ea3i l\u1edbn h\u01a1n kh\u00f4ng.<\/li>\n<\/ul>\n

                Gi\u1ea3i ph\u00e1p<\/h3>\n

                X\u00e1c \u0111\u1ecbnh c\u00e1c mi\u1ec1n ch\u00ednh x\u00e1c cho t\u1eebng thu\u1ed9c t\u00ednh trong s\u01a1 \u0111\u1ed3. X\u00e1c \u0111\u1ecbnh lo\u1ea1i d\u1eef li\u1ec7u ch\u00ednh x\u00e1c v\u00e0 b\u1ea5t k\u1ef3 gi\u1edbi h\u1ea1n \u0111\u1ed9 d\u00e0i n\u00e0o. \u0110\u1ed1i v\u1edbi c\u00e1c gi\u00e1 tr\u1ecb ti\u1ec1n t\u1ec7, h\u00e3y s\u1eed d\u1ee5ng ki\u1ec3u s\u1ed1 th\u1eadp ph\u00e2n v\u1edbi \u0111\u1ed9 ch\u00ednh x\u00e1c c\u1ed1 \u0111\u1ecbnh. \u0110\u1ed1i v\u1edbi ng\u00e0y th\u00e1ng, x\u00e1c \u0111\u1ecbnh \u0111\u1ecbnh d\u1ea1ng (YYYY-MM-DD). Bao g\u1ed3m c\u00e1c r\u00e0ng bu\u1ed9c cho c\u00e1c tr\u01b0\u1eddng b\u1eaft bu\u1ed9c v\u00e0 c\u00e1c ph\u1ea1m vi \u0111\u01b0\u1ee3c ph\u00e9p. \u0110i\u1ec1u n\u00e0y \u0111\u1ea3m b\u1ea3o r\u1eb1ng b\u1ed9 \u0111\u1ed9ng c\u01a1 c\u01a1 s\u1edf d\u1eef li\u1ec7u t\u1eeb ch\u1ed1i d\u1eef li\u1ec7u kh\u00f4ng h\u1ee3p l\u1ec7 ngay t\u1ea1i ngu\u1ed3n. \ud83d\udcb0<\/p>\n

                L\u1ed7i 5: Tham chi\u1ebfu v\u00f2ng l\u1eb7p v\u00e0 m\u1ed1i quan h\u1ec7 \u0111\u1ec7 quy \ud83c\udf00<\/h2>\n

                C\u00e1c m\u1ed1i quan h\u1ec7 \u0111\u1ec7 quy x\u1ea3y ra khi m\u1ed9t th\u1ef1c th\u1ec3 li\u00ean k\u1ebft v\u1edbi ch\u00ednh n\u00f3. M\u1ed9t v\u00ed d\u1ee5 ph\u1ed5 bi\u1ebfn l\u00e0 m\u1ed9tNh\u00e2n vi\u00ean<\/em>b\u1ea3ng n\u01a1i m\u1ed7i nh\u00e2n vi\u00ean c\u00f3 m\u1ed9tQu\u1ea3n l\u00fd<\/em>ng\u01b0\u1eddi c\u0169ng l\u00e0 m\u1ed9t nh\u00e2n vi\u00ean. M\u00f4 h\u00ecnh h\u00f3a sai \u0111i\u1ec1u n\u00e0y c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn c\u00e1c v\u00f2ng l\u1eb7p v\u00f4 h\u1ea1n ho\u1eb7c s\u1ef1 b\u1ea5t nh\u1ea5t trong d\u1eef li\u1ec7u.<\/p>\n

                V\u1ea5n \u0111\u1ec1<\/h3>\n

                C\u00e1c nh\u00e0 thi\u1ebft k\u1ebf \u0111\u00f4i khi t\u1ea1o kh\u00f3a ngo\u1ea1i m\u00e0 kh\u00f4ng x\u00e1c \u0111\u1ecbnh gi\u1edbi h\u1ea1n th\u1ee9 b\u1eadc. N\u1ebfu \u0111\u1ec7 quy kh\u00f4ng \u0111\u01b0\u1ee3c x\u1eed l\u00fd, c\u00e1c truy v\u1ea5n c\u00f3 th\u1ec3 tr\u1edf n\u00ean v\u00f4 h\u1ea1n. H\u01a1n n\u1eefa, n\u1ebfu tham chi\u1ebfu t\u1ef1 th\u00e2n cho ph\u00e9p chu tr\u00ecnh (v\u00ed d\u1ee5: A qu\u1ea3n l\u00fd B, B qu\u1ea3n l\u00fd C, C qu\u1ea3n l\u00fd A), t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u li\u00ean quan \u0111\u1ebfn c\u00e1c c\u1ea5p \u0111\u1ed9 th\u1ee9 b\u1eadc s\u1ebd b\u1ecb m\u1ea5t.<\/p>\n

                H\u1eadu qu\u1ea3<\/h3>\n
                  \n
                • H\u1ebft th\u1eddi gian truy v\u1ea5n:<\/strong>C\u00e1c truy v\u1ea5n \u0111\u1ec7 quy kh\u00f4ng c\u00f3 gi\u1edbi h\u1ea1n \u0111\u1ed9 s\u00e2u s\u1ebd khi\u1ebfn h\u1ec7 th\u1ed1ng s\u1eadp.<\/li>\n
                • Th\u1ee9 b\u1eadc kh\u00f4ng h\u1ee3p l\u1ec7:<\/strong>C\u00e1c chu\u1ed7i qu\u1ea3n l\u00fd v\u00f2ng l\u1eb7p g\u00e2y nh\u1ea7m l\u1eabn trong c\u1ea5u tr\u00fac b\u00e1o c\u00e1o.<\/li>\n
                • S\u1ef1 m\u01a1 h\u1ed3 v\u1ec1 d\u1eef li\u1ec7u:<\/strong>S\u1ebd kh\u00f4ng r\u00f5 ai l\u00e0 g\u1ed1c c\u1ee7a th\u1ee9 b\u1eadc.<\/li>\n<\/ul>\n

                  Gi\u1ea3i ph\u00e1p<\/h3>\n

                  X\u00e1c \u0111\u1ecbnh m\u1ed1i quan h\u1ec7 \u0111\u1ec7 quy m\u1ed9t c\u00e1ch c\u1ea9n th\u1eadn. \u0110\u1ea3m b\u1ea3o kh\u00f3a ngo\u1ea1i c\u00f3 th\u1ec3 \u0111\u1ec3 tr\u1ed1ng \u0111\u1ec3 cho ph\u00e9p c\u00e1c n\u00fat g\u1ed1c (nh\u01b0 CEO). Tri\u1ec3n khai c\u00e1c ki\u1ec3m tra \u1edf c\u1ea5p \u0111\u1ed9 \u1ee9ng d\u1ee5ng ho\u1eb7c c\u1ea5p \u0111\u1ed9 c\u01a1 s\u1edf d\u1eef li\u1ec7u \u0111\u1ec3 ng\u0103n ch\u1eb7n chu tr\u00ecnh. S\u1eed d\u1ee5ng c\u00e1c c\u1ed9t \u0111\u1ed9 s\u00e2u ho\u1eb7c chu\u1ed7i \u0111\u01b0\u1eddng \u0111i n\u1ebfu c\u1ea7n duy\u1ec7t th\u1ee9 b\u1eadc ph\u1ee9c t\u1ea1p. Ghi ch\u00fa \u0111\u1ed9 s\u00e2u t\u1ed1i \u0111a c\u1ee7a th\u1ee9 b\u1eadc trong t\u00e0i li\u1ec7u thi\u1ebft k\u1ebf. \ud83d\udc64<\/p>\n

                  L\u1ed7i 6: Thi\u1ebfu r\u00e0ng bu\u1ed9c duy nh\u1ea5t tr\u00ean kh\u00f3a ch\u00ednh \ud83d\udd11<\/h2>\n

                  Kh\u00f3a ch\u00ednh l\u00e0 \u0111\u1ecbnh danh duy nh\u1ea5t cho m\u1ed9t b\u1ea3n ghi. \u0110\u00f3 l\u00e0 n\u1ec1n t\u1ea3ng c\u1ee7a t\u00ednh to\u00e0n v\u1eb9n th\u1ef1c th\u1ec3. N\u1ebfu kh\u00f3a ch\u00ednh kh\u00f4ng \u0111\u01b0\u1ee3c \u0111\u1ea3m b\u1ea3o l\u00e0 duy nh\u1ea5t, c\u00e1c b\u1ea3n ghi tr\u00f9ng l\u1eb7p c\u00f3 th\u1ec3 t\u1ed3n t\u1ea1i.<\/p>\n

                  V\u1ea5n \u0111\u1ec1<\/h3>\n

                  M\u1ed9t s\u1ed1 m\u00f4 h\u00ecnh \u0111\u1ec1 xu\u1ea5t kh\u00f3a gi\u1ea3 (nh\u01b0 ID t\u1ef1 t\u0103ng) nh\u01b0ng l\u1ea1i kh\u00f4ng \u0111\u00e1nh d\u1ea5u n\u00f3 l\u00e0 kh\u00f3a ch\u00ednh trong s\u01a1 \u0111\u1ed3. Ho\u1eb7c thay v\u00e0o \u0111\u00f3, c\u00e1c kh\u00f3a t\u1ef1 nhi\u00ean (nh\u01b0 S\u1ed1 b\u1ea3o hi\u1ec3m x\u00e3 h\u1ed9i) \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng m\u00e0 kh\u00f4ng c\u00f3 r\u00e0ng bu\u1ed9c duy nh\u1ea5t. \u0110i\u1ec1u n\u00e0y cho ph\u00e9p c\u01a1 s\u1edf d\u1eef li\u1ec7u ch\u1ea5p nh\u1eadn c\u00e1c b\u1ea3n ghi tr\u00f9ng l\u1eb7p cho c\u00f9ng m\u1ed9t th\u1ef1c th\u1ec3 logic.<\/p>\n

                  H\u1eadu qu\u1ea3<\/h3>\n
                    \n
                  • D\u1eef li\u1ec7u tr\u00f9ng l\u1eb7p:<\/strong>C\u00f9ng m\u1ed9t kh\u00e1ch h\u00e0ng ho\u1eb7c s\u1ea3n ph\u1ea9m xu\u1ea5t hi\u1ec7n nhi\u1ec1u l\u1ea7n.<\/li>\n
                  • S\u1ef1 nh\u1ea7m l\u1eabn khi c\u1eadp nh\u1eadt:<\/strong>C\u00e1c thao t\u00e1c c\u1eadp nh\u1eadt c\u00f3 th\u1ec3 ch\u1ec9 \u00e1p d\u1ee5ng cho m\u1ed9t trong c\u00e1c b\u1ea3n ghi tr\u00f9ng l\u1eb7p.<\/li>\n
                  • S\u1ef1 m\u01a1 h\u1ed3 khi n\u1ed1i k\u1ebft:<\/strong>C\u00e1c truy v\u1ea5n n\u1ed1i k\u1ebft theo kh\u00f3a c\u00f3 th\u1ec3 tr\u1ea3 v\u1ec1 nhi\u1ec1u h\u00e0ng m\u1ed9t c\u00e1ch b\u1ea5t ng\u1edd.<\/li>\n<\/ul>\n

                    Gi\u1ea3i ph\u00e1p<\/h3>\n

                    Lu\u00f4n x\u00e1c \u0111\u1ecbnh r\u00f5 r\u00e0ng kh\u00f3a ch\u00ednh trong s\u01a1 \u0111\u1ed3 ERD. \u0110\u00e1nh d\u1ea5u n\u00f3 b\u1eb1ng bi\u1ec3u t\u01b0\u1ee3ng kh\u00f3a ho\u1eb7c k\u00fd hi\u1ec7u c\u1ee5 th\u1ec3. \u0110\u1ea3m b\u1ea3o c\u1ed9t \u0111\u01b0\u1ee3c \u0111\u1ecbnh ngh\u0129a l\u00e0 NOT NULL. N\u1ebfu s\u1eed d\u1ee5ng kh\u00f3a t\u1ef1 nhi\u00ean, h\u00e3y th\u00eam r\u00e0ng bu\u1ed9c duy nh\u1ea5t \u0111\u1ec3 ng\u0103n ch\u1eb7n c\u00e1c b\u1ea3n ghi tr\u00f9ng l\u1eb7p. \u0110\u1ed1i v\u1edbi kh\u00f3a gi\u1ea3, \u0111\u1ea3m b\u1ea3o c\u01a1 ch\u1ebf sinh ra kh\u00f3a n\u00e0y \u0111\u00e1ng tin c\u1eady v\u00e0 kh\u00f4ng xung \u0111\u1ed9t. \ud83d\udd12<\/p>\n

                    L\u1ed7i 7: Quy \u01b0\u1edbc \u0111\u1eb7t t\u00ean kh\u00f4ng nh\u1ea5t qu\u00e1n \ud83c\udff7\ufe0f<\/h2>\n

                    M\u1eb7c d\u00f9 \u0111i\u1ec1u n\u00e0y c\u00f3 v\u1ebb ch\u1ec9 mang t\u00ednh th\u1ea9m m\u1ef9, nh\u01b0ng quy \u01b0\u1edbc \u0111\u1eb7t t\u00ean tr\u1ef1c ti\u1ebfp \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u. Nh\u1eefng t\u00ean kh\u00f4ng nh\u1ea5t qu\u00e1n d\u1eabn \u0111\u1ebfn s\u1ef1 nh\u1ea7m l\u1eabn v\u00e0 t\u1ea1o ra c\u00e1c th\u1ef1c th\u1ec3 tr\u00f9ng l\u1eb7p.<\/p>\n

                    V\u1ea5n \u0111\u1ec1<\/h3>\n

                    M\u1ed9t b\u1ea3ng c\u00f3 th\u1ec3 s\u1eed d\u1ee5nguser_id<\/code>, trong khi b\u1ea3ng kh\u00e1c l\u1ea1i s\u1eed d\u1ee5ngUserID<\/code> ho\u1eb7cuserIdentifier<\/code>. Khi c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n x\u00e2y d\u1ef1ng truy v\u1ea5n, h\u1ecd c\u00f3 th\u1ec3 nh\u1ea7m l\u1eabn gi\u1eefa c\u00e1c t\u00ean n\u00e0y. H\u1ecd c\u00f3 th\u1ec3 n\u1ed1i (join) tr\u00ean c\u1ed9t sai ho\u1eb7c t\u1ea1o ra c\u00e1c c\u1ed9t m\u1edbi tr\u00f9ng l\u1eb7p d\u1eef li\u1ec7u hi\u1ec7n c\u00f3 v\u00ec kh\u00f4ng nh\u1eadn ra r\u1eb1ng ch\u00fang l\u00e0 t\u1eeb \u0111\u1ed3ng ngh\u0129a.<\/p>\n

                    H\u1eadu qu\u1ea3<\/h3>\n
                      \n
                    • Th\u1ea5t b\u1ea1i t\u00edch h\u1ee3p:<\/strong>D\u1eef li\u1ec7u t\u1eeb c\u00e1c m\u00f4-\u0111un kh\u00e1c nhau kh\u00f4ng th\u1ec3 \u0111\u01b0\u1ee3c n\u1ed1i \u0111\u00fang c\u00e1ch.<\/li>\n
                    • G\u00e1nh n\u1eb7ng b\u1ea3o tr\u00ec:<\/strong>C\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n ph\u1ea3i t\u1ed1n th\u1eddi gian \u0111\u1ec3 gi\u1ea3i m\u00e3 \u00fd ngh\u0129a c\u1ee7a t\u1eebng c\u1ed9t.<\/li>\n
                    • S\u1ef1 l\u1ec7ch chu\u1ea9n c\u1ea5u tr\u00fac:<\/strong>Theo th\u1eddi gian, c\u1ea5u tr\u00fac c\u01a1 s\u1edf d\u1eef li\u1ec7u tr\u1edf n\u00ean ph\u00e2n m\u1ea3nh v\u00e0 kh\u00f4ng nh\u1ea5t qu\u00e1n.<\/li>\n<\/ul>\n

                      Gi\u1ea3i ph\u00e1p<\/h3>\n

                      Thi\u1ebft l\u1eadp m\u1ed9t ti\u00eau chu\u1ea9n \u0111\u1eb7t t\u00ean nghi\u00eam ng\u1eb7t. S\u1eed d\u1ee5ng ch\u1eef th\u01b0\u1eddng c\u00f3 d\u1ea5u g\u1ea1ch d\u01b0\u1edbi cho t\u00ean c\u1ed9t. S\u1eed d\u1ee5ng danh t\u1eeb s\u1ed1 nhi\u1ec1u cho t\u00ean b\u1ea3ng (v\u00ed d\u1ee5,orders<\/code>, kh\u00f4ng ph\u1ea3iorder<\/code>). \u0110\u1ea3m b\u1ea3o r\u1eb1ng c\u00e1c th\u1ef1c th\u1ec3 li\u00ean quan s\u1eed d\u1ee5ng c\u00f9ng m\u1ed9t t\u00ean kh\u00f3a ngo\u1ea1i. Ghi ch\u00e9p c\u00e1c quy \u01b0\u1edbc n\u00e0y trong t\u1eeb \u0111i\u1ec3n d\u1eef li\u1ec7u. S\u1ef1 nh\u1ea5t qu\u00e1n n\u00e0y gi\u00fap gi\u1ea3m t\u1ea3i nh\u1eadn th\u1ee9c cho c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n v\u00e0 h\u1ea1n ch\u1ebf sai s\u00f3t. \ud83d\udcd6<\/p>\n

                      T\u00f3m t\u1eaft c\u00e1c l\u1ed7i m\u00f4 h\u00ecnh h\u00f3a ph\u1ed5 bi\u1ebfn<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n
                      Lo\u1ea1i l\u1ed7i<\/th>\nR\u1ee7i ro ch\u00ednh<\/th>\nGi\u1ea3i ph\u00e1p \u0111\u01b0\u1ee3c khuy\u1ebfn ngh\u1ecb<\/th>\n<\/tr>\n<\/thead>\n
                      \u0110\u1ed9 b\u1ed9i kh\u00f4ng r\u00f5 r\u00e0ng<\/td>\nTh\u1eeba d\u01b0 ho\u1eb7c gi\u1edbi h\u1ea1n d\u1eef li\u1ec7u<\/td>\nX\u00e1c \u0111\u1ecbnh r\u00f5 r\u00e0ng c\u00e1c m\u1ed1i quan h\u1ec7 1:1, 1:N, M:N<\/td>\n<\/tr>\n
                      Thi\u1ebfu kh\u00f3a ngo\u1ea1i<\/td>\nC\u00e1c b\u1ea3n ghi b\u1ecb b\u1ecf r\u01a1i<\/td>\nTh\u1ef1c thi c\u00e1c r\u00e0ng bu\u1ed9c to\u00e0n v\u1eb9n tham chi\u1ebfu<\/td>\n<\/tr>\n
                      Chu\u1ea9n h\u00f3a k\u00e9m<\/td>\nSai s\u00f3t c\u1eadp nh\u1eadt\/ ch\u00e8n d\u1eef li\u1ec7u<\/td>\n\u00c1p d\u1ee5ng c\u00e1c quy t\u1eafc 1NF, 2NF, 3NF<\/td>\n<\/tr>\n
                      Lo\u1ea1i d\u1eef li\u1ec7u sai<\/td>\nL\u1ed7i t\u00ednh to\u00e1n v\u00e0 x\u00e1c th\u1ef1c<\/td>\nX\u00e1c \u0111\u1ecbnh r\u00f5 r\u00e0ng mi\u1ec1n v\u00e0 ki\u1ec3u d\u1eef li\u1ec7u<\/td>\n<\/tr>\n
                      V\u00f2ng l\u1eb7p \u0111\u1ec7 quy<\/td>\nH\u1ebft th\u1eddi gian truy v\u1ea5n<\/td>\nGi\u1edbi h\u1ea1n \u0111\u1ed9 s\u00e2u ph\u00e2n c\u1ea5p v\u00e0 ki\u1ec3m tra chu tr\u00ecnh<\/td>\n<\/tr>\n
                      Kh\u00f3a ch\u00ednh y\u1ebfu<\/td>\nC\u00e1c b\u1ea3n ghi tr\u00f9ng l\u1eb7p<\/td>\nTh\u1ef1c thi duy nh\u1ea5t + KH\u00d4NG R\u1ed6NG<\/td>\n<\/tr>\n
                      T\u00ean g\u1ecdi kh\u00f4ng nh\u1ea5t qu\u00e1n<\/td>\nTh\u1ea5t b\u1ea1i t\u00edch h\u1ee3p<\/td>\n\u00c1p d\u1ee5ng ti\u00eau chu\u1ea9n \u0111\u1eb7t t\u00ean nghi\u00eam ng\u1eb7t<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

                      Chi\u1ebfn l\u01b0\u1ee3c thi\u1ebft k\u1ebf ERD b\u1ec1n v\u1eefng \ud83d\udee0\ufe0f<\/h2>\n

                      Ng\u0103n ch\u1eb7n nh\u1eefng sai l\u1ea7m n\u00e0y \u0111\u00f2i h\u1ecfi c\u00e1ch ti\u1ebfp c\u1eadn k\u1ef7 lu\u1eadt. Ch\u1ec9 v\u1ebd c\u00e1c \u0111\u01b0\u1eddng n\u1ed1i l\u00e0 ch\u01b0a \u0111\u1ee7; b\u1ea1n ph\u1ea3i x\u00e1c minh t\u00ednh logic. D\u01b0\u1edbi \u0111\u00e2y l\u00e0 c\u00e1c chi\u1ebfn l\u01b0\u1ee3c \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o m\u00f4 h\u00ecnh c\u1ee7a b\u1ea1n ch\u1ecbu \u0111\u01b0\u1ee3c s\u1ef1 ki\u1ec3m tra k\u1ef9 l\u01b0\u1ee1ng.<\/p>\n

                        \n
                      • Xem x\u00e9t b\u1edfi \u0111\u1ed3ng nghi\u1ec7p:<\/strong> H\u00e3y \u0111\u1ec3 m\u1ed9t ki\u1ebfn tr\u00fac s\u01b0 kh\u00e1c xem x\u00e9t s\u01a1 \u0111\u1ed3. Nh\u1eefng \u0111\u00f4i m\u1eaft m\u1edbi th\u01b0\u1eddng ph\u00e1t hi\u1ec7n ra nh\u1eefng kho\u1ea3ng tr\u1ed1ng logic m\u00e0 ng\u01b0\u1eddi t\u1ea1o ra b\u1ecf s\u00f3t.<\/li>\n
                      • Ki\u1ec3m th\u1eed d\u1eef li\u1ec7u gi\u1ea3:<\/strong> Tr\u01b0\u1edbc khi tri\u1ec3n khai, \u0111i\u1ec1n d\u1eef li\u1ec7u m\u1eabu v\u00e0o c\u01a1 s\u1edf d\u1eef li\u1ec7u ki\u1ec3m th\u1eed. Th\u1eed vi ph\u1ea1m c\u00e1c quy t\u1eafc b\u1ea1n \u0111\u00e3 thi\u1ebft k\u1ebf. Xem h\u1ec7 th\u1ed1ng c\u00f3 ng\u0103n b\u1ea1n l\u1ea1i hay kh\u00f4ng.<\/li>\n
                      • T\u00e0i li\u1ec7u:<\/strong> Vi\u1ebft t\u1eeb \u0111i\u1ec3n d\u1eef li\u1ec7u song song v\u1edbi ERD. Gi\u1ea3i th\u00edch quy t\u1eafc kinh doanh \u0111\u1eb1ng sau m\u1ed7i m\u1ed1i quan h\u1ec7 v\u00e0 r\u00e0ng bu\u1ed9c.<\/li>\n
                      • Thi\u1ebft k\u1ebf theo t\u1eebng b\u01b0\u1edbc l\u1eb7p:<\/strong> \u0110\u1eebng mong phi\u00ean b\u1ea3n \u0111\u1ea7u ti\u00ean l\u00e0 ho\u00e0n h\u1ea3o. Tinh ch\u1ec9nh m\u00f4 h\u00ecnh khi y\u00eau c\u1ea7u kinh doanh thay \u0111\u1ed5i.<\/li>\n<\/ul>\n

                        C\u00e1c k\u1ef9 thu\u1eadt x\u00e1c minh tr\u01b0\u1edbc khi tri\u1ec3n khai \ud83e\uddea<\/h2>\n

                        Sau khi ERD \u0111\u01b0\u1ee3c ho\u00e0n thi\u1ec7n, b\u01b0\u1edbc x\u00e1c minh l\u00e0 b\u01b0\u1edbc ti\u1ebfp theo quan tr\u1ecdng. Qu\u00e1 tr\u00ecnh n\u00e0y \u0111\u1ea3m b\u1ea3o r\u1eb1ng thi\u1ebft k\u1ebf \u0111\u01b0\u1ee3c chuy\u1ec3n \u0111\u1ed5i ch\u00ednh x\u00e1c th\u00e0nh l\u01b0\u1ee3c \u0111\u1ed3 v\u1eadt l\u00fd.<\/p>\n

                          \n
                        1. T\u1ea1o script:<\/strong>S\u1eed d\u1ee5ng c\u00f4ng c\u1ee5 \u0111\u1ec3 t\u1ea1o c\u00e1c script SQL t\u1eeb s\u01a1 \u0111\u1ed3. Ki\u1ec3m tra script \u0111\u00e3 t\u1ea1o \u0111\u1ec3 ph\u00e1t hi\u1ec7n l\u1ed7i c\u00fa ph\u00e1p ho\u1eb7c c\u00e1c r\u00e0ng bu\u1ed9c b\u1ecb thi\u1ebfu.<\/li>\n
                        2. X\u00e1c minh r\u00e0ng bu\u1ed9c:<\/strong>Ki\u1ec3m tra xem m\u1ed7i kh\u00f3a ngo\u1ea1i trong script c\u00f3 kh\u1edbp v\u1edbi kh\u00f3a ch\u00ednh trong b\u1ea3ng cha hay kh\u00f4ng.<\/li>\n
                        3. Ph\u00e2n t\u00edch ch\u1ec9 m\u1ee5c:<\/strong>\u0110\u1ea3m b\u1ea3o r\u1eb1ng c\u00e1c kh\u00f3a ngo\u1ea1i v\u00e0 r\u00e0ng bu\u1ed9c duy nh\u1ea5t \u0111\u01b0\u1ee3c ch\u1ec9 m\u1ee5c \u0111\u1ec3 t\u1ed1i \u01b0u hi\u1ec7u su\u1ea5t.<\/li>\n
                        4. Xem x\u00e9t c\u00e1c tr\u01b0\u1eddng h\u1ee3p bi\u00ean:<\/strong>Xem x\u00e9t c\u00e1c gi\u00e1 tr\u1ecb null. M\u1ed9t tr\u01b0\u1eddng b\u1eaft bu\u1ed9c c\u00f3 th\u1ec3 l\u00e0 null trong thi\u1ebft k\u1ebf c\u1ee7a b\u1ea1n kh\u00f4ng? N\u1ebfu kh\u00f4ng, h\u00e3y \u0111\u00e1nh d\u1ea5u r\u00f5 r\u00e0ng l\u00e0 NOT NULL.<\/li>\n<\/ol>\n

                          Giai \u0111o\u1ea1n n\u00e0y ph\u00e1t hi\u1ec7n c\u00e1c l\u1ed7i tri\u1ec3n khai kh\u00f4ng xu\u1ea5t hi\u1ec7n trong s\u01a1 \u0111\u1ed3 tr\u1ef1c quan. N\u00f3 l\u1ea5p \u0111\u1ea7y kho\u1ea3ng c\u00e1ch gi\u1eefa l\u00fd thuy\u1ebft v\u00e0 th\u1ef1c t\u1ebf. \ud83d\udd2c<\/p>\n

                          Duy tr\u00ec l\u01b0\u1ee3c \u0111\u1ed3 theo th\u1eddi gian \ud83d\udd04<\/h2>\n

                          Thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u kh\u00f4ng ph\u1ea3i l\u00e0 m\u1ed9t s\u1ef1 ki\u1ec7n duy nh\u1ea5t. Y\u00eau c\u1ea7u thay \u0111\u1ed5i, v\u00e0 l\u01b0\u1ee3c \u0111\u1ed3 ph\u1ea3i ph\u00e1t tri\u1ec3n m\u00e0 kh\u00f4ng l\u00e0m h\u1ecfng t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u hi\u1ec7n t\u1ea1i. Khi s\u1eeda \u0111\u1ed5i ERD, h\u00e3y tu\u00e2n theo c\u00e1c h\u01b0\u1edbng d\u1eabn sau.<\/p>\n

                            \n
                          • Ki\u1ec3m so\u00e1t phi\u00ean b\u1ea3n:<\/strong>Gi\u1eef l\u1ecbch s\u1eed thay \u0111\u1ed5i l\u01b0\u1ee3c \u0111\u1ed3. \u0110i\u1ec1u n\u00e0y cho ph\u00e9p b\u1ea1n ho\u00e0n nguy\u00ean n\u1ebfu m\u1ed9t thay \u0111\u1ed5i g\u00e2y ra l\u1ed7i.<\/li>\n
                          • T\u00ednh t\u01b0\u01a1ng th\u00edch ng\u01b0\u1ee3c:<\/strong>Khi th\u00eam c\u1ed9t, h\u00e3y cho ph\u00e9p ch\u00fang c\u00f3 th\u1ec3 null ban \u0111\u1ea7u. Kh\u00f4ng l\u00e0m h\u1ecfng c\u00e1c truy v\u1ea5n hi\u1ec7n t\u1ea1i kh\u00f4ng mong \u0111\u1ee3i d\u1eef li\u1ec7u m\u1edbi.<\/li>\n
                          • Script di chuy\u1ec3n:<\/strong>Kh\u00f4ng bao gi\u1edd thay \u0111\u1ed5i tr\u1ef1c ti\u1ebfp m\u1ed9t b\u1ea3ng trong m\u00f4i tr\u01b0\u1eddng s\u1ea3n xu\u1ea5t m\u00e0 kh\u00f4ng c\u00f3 script di chuy\u1ec3n. C\u00e1c script \u0111\u1ea3m b\u1ea3o thay \u0111\u1ed5i c\u00f3 th\u1ec3 t\u00e1i t\u1ea1o v\u00e0 an to\u00e0n.<\/li>\n
                          • Giao ti\u1ebfp:<\/strong>Th\u00f4ng b\u00e1o cho c\u00e1c \u0111\u1ed9i \u1ee9ng d\u1ee5ng v\u1ec1 c\u00e1c thay \u0111\u1ed5i l\u01b0\u1ee3c \u0111\u1ed3. H\u1ecd ph\u1ea3i c\u1eadp nh\u1eadt m\u00e3 c\u1ee7a m\u00ecnh \u0111\u1ec3 ph\u00f9 h\u1ee3p v\u1edbi c\u1ea5u tr\u00fac m\u1edbi.<\/li>\n<\/ul>\n

                            B\u1eb1ng c\u00e1ch coi ERD nh\u01b0 m\u1ed9t t\u00e0i li\u1ec7u s\u1ed1ng, b\u1ea1n \u0111\u1ea3m b\u1ea3o r\u1eb1ng t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c duy tr\u00ec xuy\u00ean su\u1ed1t v\u00f2ng \u0111\u1eddi ph\u1ea7n m\u1ec1m. T\u00ednh nh\u1ea5t qu\u00e1n l\u00e0 ch\u00eca kh\u00f3a cho \u0111\u1ed9 tin c\u1eady l\u00e2u d\u00e0i. \ud83d\udcc8<\/p>\n

                            X\u1eed l\u00fd di chuy\u1ec3n d\u1eef li\u1ec7u c\u0169 \ud83d\udd04<\/h2>\n

                            \u0110\u00f4i khi, b\u1ea1n ph\u1ea3i di chuy\u1ec3n d\u1eef li\u1ec7u v\u00e0o m\u1ed9t c\u1ea5u tr\u00fac m\u1edbi tu\u00e2n theo c\u00e1c quy t\u1eafc to\u00e0n v\u1eb9n t\u1ed1t h\u01a1n. Qu\u00e1 tr\u00ecnh n\u00e0y mang l\u1ea1i nh\u1eefng r\u1ee7i ro c\u1ee5 th\u1ec3.<\/p>\n

                              \n
                            • L\u00e0m s\u1ea1ch d\u1eef li\u1ec7u:<\/strong>Tr\u01b0\u1edbc khi di chuy\u1ec3n, l\u00e0m s\u1ea1ch d\u1eef li\u1ec7u ngu\u1ed3n. Lo\u1ea1i b\u1ecf c\u00e1c b\u1ea3n sao v\u00e0 s\u1eeda l\u1ed7i \u0111\u1ecbnh d\u1ea1ng.<\/li>\n
                            • X\u00e1c minh \u00e1nh x\u1ea1:<\/strong>\u0110\u1ea3m b\u1ea3o m\u1ed7i tr\u01b0\u1eddng ngu\u1ed3n \u0111\u01b0\u1ee3c \u00e1nh x\u1ea1 v\u00e0o m\u1ed9t tr\u01b0\u1eddng \u0111\u00edch h\u1ee3p l\u1ec7 v\u1edbi ki\u1ec3u d\u1eef li\u1ec7u \u0111\u00fang.<\/li>\n
                            • Ki\u1ec3m th\u1eed r\u00e0ng bu\u1ed9c:<\/strong>Ch\u1ea1y c\u00e1c r\u00e0ng bu\u1ed9c to\u00e0n v\u1eb9n tr\u00ean d\u1eef li\u1ec7u \u0111\u00e3 di chuy\u1ec3n tr\u01b0\u1edbc khi \u0111\u01b0a n\u00f3 v\u00e0o ho\u1ea1t \u0111\u1ed9ng.<\/li>\n
                            • K\u1ebf ho\u1ea1ch ho\u00e0n t\u00e1c:<\/strong>C\u00f3 m\u1ed9t k\u1ebf ho\u1ea1ch \u0111\u1ec3 quay l\u1ea1i h\u1ec7 th\u1ed1ng c\u0169 n\u1ebfu qu\u00e1 tr\u00ecnh di d\u1eddi th\u1ea5t b\u1ea1i ho\u1eb7c l\u00e0m h\u1ecfng d\u1eef li\u1ec7u.<\/li>\n<\/ul>\n

                              C\u00e1c vi ph\u1ea1m t\u00ednh to\u00e0n v\u1eb9n r\u1ea5t t\u1ed1n k\u00e9m khi s\u1eeda sau tri\u1ec3n khai. Ng\u0103n ch\u1eb7n ch\u00fang \u1edf giai \u0111o\u1ea1n m\u00f4 h\u00ecnh h\u00f3a s\u1ebd ti\u1ebft ki\u1ec7m th\u1eddi gian, ti\u1ec1n b\u1ea1c v\u00e0 ni\u1ec1m tin t\u1eeb ng\u01b0\u1eddi d\u00f9ng. T\u1eadp trung v\u00e0o \u0111\u1ed9 ch\u00ednh x\u00e1c, s\u1ef1 r\u00f5 r\u00e0ng v\u00e0 tu\u00e2n th\u1ee7 l\u00fd thuy\u1ebft quan h\u1ec7. M\u1ed9t n\u1ec1n t\u1ea3ng v\u1eefng ch\u1eafc s\u1ebd h\u1ed7 tr\u1ee3 m\u1ecdi ph\u00e1t tri\u1ec3n trong t\u01b0\u01a1ng lai. \ud83c\udfdb\ufe0f<\/p>\n","protected":false},"excerpt":{"rendered":"

                              Thi\u1ebft k\u1ebf m\u1ed9t c\u1ea5u tr\u00fac c\u01a1 s\u1edf d\u1eef li\u1ec7u m\u1ea1nh m\u1ebd b\u1eaft \u0111\u1ea7u b\u1eb1ng m\u1ed9t k\u1ebf ho\u1ea1ch ch\u00ednh x\u00e1c. S\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 (ERD) \u0111\u00f3ng vai tr\u00f2 nh\u01b0…<\/p>\n","protected":false},"author":1,"featured_media":1642,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_yoast_wpseo_title":"H\u01b0\u1edbng d\u1eabn v\u1ec1 sai l\u1ea7m trong m\u00f4 h\u00ecnh h\u00f3a ERD v\u00e0 c\u00e1c vi ph\u1ea1m t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u \ud83d\udcca","_yoast_wpseo_metadesc":"H\u1ecdc c\u00e1ch tr\u00e1nh c\u00e1c l\u1ed7i ph\u1ed5 bi\u1ebfn trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3. Ng\u0103n ch\u1eb7n c\u00e1c vi ph\u1ea1m t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u b\u1eb1ng c\u00e1c nguy\u00ean t\u1eafc thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u1eefng ch\u1eafc v\u00e0 c\u00e1c th\u1ef1c h\u00e0nh t\u1ed1t nh\u1ea5t.","fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[68],"tags":[89,92],"class_list":["post-1641","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-database-design","tag-academic","tag-erd"],"yoast_head":"\nH\u01b0\u1edbng d\u1eabn v\u1ec1 sai l\u1ea7m trong m\u00f4 h\u00ecnh h\u00f3a ERD v\u00e0 c\u00e1c vi ph\u1ea1m t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u \ud83d\udcca<\/title>\n<meta name=\"description\" content=\"H\u1ecdc c\u00e1ch tr\u00e1nh c\u00e1c l\u1ed7i ph\u1ed5 bi\u1ebfn trong s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3. 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