{"id":1618,"date":"2026-03-26T01:48:41","date_gmt":"2026-03-26T01:48:41","guid":{"rendered":"https:\/\/www.ez-knowledge.com\/vi\/enforcing-data-integrity-erd-constraints\/"},"modified":"2026-03-26T01:48:41","modified_gmt":"2026-03-26T01:48:41","slug":"enforcing-data-integrity-erd-constraints","status":"publish","type":"post","link":"https:\/\/www.ez-knowledge.com\/vi\/enforcing-data-integrity-erd-constraints\/","title":{"rendered":"Th\u1ef1c thi to\u00e0n v\u1eb9n d\u1eef li\u1ec7u th\u00f4ng qua c\u00e1c r\u00e0ng bu\u1ed9c ERD nghi\u00eam ng\u1eb7t"},"content":{"rendered":"
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\"Kawaii-style<\/figure>\n<\/div>\n

Trong ki\u1ebfn tr\u00fac d\u1eef li\u1ec7u hi\u1ec7n \u0111\u1ea1i, \u0111\u1ed9 tin c\u1eady c\u1ee7a th\u00f4ng tin ph\u1ee5 thu\u1ed9c v\u00e0o c\u00e1c bi\u1ec7n ph\u00e1p b\u1ea3o v\u1ec7 c\u1ea5u tr\u00fac \u0111\u01b0\u1ee3c x\u00e2y d\u1ef1ng trong giai \u0111o\u1ea1n thi\u1ebft k\u1ebf. To\u00e0n v\u1eb9n d\u1eef li\u1ec7u kh\u00f4ng ph\u1ea3i l\u00e0 \u0111i\u1ec1u \u0111\u01b0\u1ee3c xem x\u00e9t sau c\u00f9ng; n\u00f3 l\u00e0 n\u1ec1n t\u1ea3ng c\u1ee7a c\u00e1c h\u1ec7 th\u1ed1ng \u0111\u00e1ng tin c\u1eady. Khi thi\u1ebft k\u1ebf s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 (ERD), m\u1ee5c ti\u00eau l\u00e0 t\u1ea1o ra m\u1ed9t b\u1ea3n v\u1ebd thi\u1ebft k\u1ebf v\u1ed1n \u0111\u00e3 ng\u0103n ng\u1eeba \u0111\u01b0\u1ee3c s\u1ef1 h\u1ecfng h\u00f3c, b\u1ea5t nh\u1ea5t v\u00e0 m\u1ea5t m\u00e1t d\u1eef li\u1ec7u. B\u1eb1ng c\u00e1ch \u00e1p d\u1ee5ng c\u00e1c r\u00e0ng bu\u1ed9c nghi\u00eam ng\u1eb7t, c\u00e1c ki\u1ebfn tr\u00fac s\u01b0 \u0111\u1ea3m b\u1ea3o c\u01a1 s\u1edf d\u1eef li\u1ec7u ho\u1ea1t \u0111\u1ed9ng m\u1ed9t c\u00e1ch d\u1ef1 \u0111o\u00e1n \u0111\u01b0\u1ee3c d\u01b0\u1edbi t\u1ea3i tr\u1ecdng v\u00e0 trong su\u1ed1t c\u00e1c giao d\u1ecbch.<\/p>\n

Kh\u00f4ng c\u00f3 nh\u1eefng quy t\u1eafc \u0111\u01b0\u1ee3c th\u1ef1c thi n\u00e0y, d\u1eef li\u1ec7u s\u1ebd d\u1ec5 b\u1ecb t\u1ed5n th\u01b0\u01a1ng do l\u1ed7i con ng\u01b0\u1eddi, l\u1ed7i \u1ee9ng d\u1ee5ng v\u00e0 c\u00e1c v\u1ea5n \u0111\u1ec1 truy c\u1eadp \u0111\u1ed3ng th\u1eddi. M\u1ed9t s\u01a1 \u0111\u1ed3 ERD \u0111\u01b0\u1ee3c c\u1ea5u tr\u00fac t\u1ed1t \u0111\u00f3ng vai tr\u00f2 nh\u01b0 m\u1ed9t h\u1ee3p \u0111\u1ed3ng gi\u1eefa logic \u1ee9ng d\u1ee5ng v\u00e0 l\u1edbp l\u01b0u tr\u1eef, x\u00e1c \u0111\u1ecbnh \u0111i\u1ec1u g\u00ec \u0111\u01b0\u1ee3c ph\u00e9p v\u00e0 \u0111i\u1ec1u g\u00ec b\u1ecb c\u1ea5m. B\u00e0i vi\u1ebft n\u00e0y chi ti\u1ebft c\u00e1c c\u01a1 ch\u1ebf duy tr\u00ec t\u00ednh nh\u1ea5t qu\u00e1n th\u00f4ng qua c\u00e1c nguy\u00ean t\u1eafc thi\u1ebft k\u1ebf nghi\u00eam ng\u1eb7t.<\/p>\n

Hi\u1ec3u r\u00f5 c\u00e1c l\u1edbp c\u1ee7a to\u00e0n v\u1eb9n d\u1eef li\u1ec7u \ud83d\udd0d<\/h2>\n

To\u00e0n v\u1eb9n kh\u00f4ng ph\u1ea3i l\u00e0 m\u1ed9t kh\u00e1i ni\u1ec7m duy nh\u1ea5t m\u00e0 l\u00e0 t\u1eadp h\u1ee3p c\u00e1c quy t\u1eafc \u00e1p d\u1ee5ng \u1edf c\u00e1c m\u1ee9c \u0111\u1ed9 kh\u00e1c nhau trong c\u1ea5u tr\u00fac c\u01a1 s\u1edf d\u1eef li\u1ec7u. Vi\u1ec7c nh\u1eadn di\u1ec7n c\u00e1c l\u1edbp n\u00e0y cho ph\u00e9p tri\u1ec3n khai c\u00e1c r\u00e0ng bu\u1ed9c m\u1ed9t c\u00e1ch ch\u00ednh x\u00e1c.<\/p>\n

1. To\u00e0n v\u1eb9n th\u1ef1c th\u1ec3<\/h3>\n

To\u00e0n v\u1eb9n th\u1ef1c th\u1ec3 \u0111\u1ea3m b\u1ea3o r\u1eb1ng m\u1ed7i h\u00e0ng trong b\u1ea3ng \u0111\u1ec1u c\u00f3 th\u1ec3 x\u00e1c \u0111\u1ecbnh duy nh\u1ea5t. \u0110\u00e2y l\u00e0 y\u00eau c\u1ea7u c\u01a1 b\u1ea3n nh\u1ea5t \u0111\u1ed1i v\u1edbi b\u1ea5t k\u1ef3 m\u00f4 h\u00ecnh quan h\u1ec7 n\u00e0o. Kh\u00f4ng c\u00f3 vi\u1ec7c x\u00e1c \u0111\u1ecbnh duy nh\u1ea5t, vi\u1ec7c theo d\u00f5i thay \u0111\u1ed5i ho\u1eb7c m\u1ed1i quan h\u1ec7 s\u1ebd tr\u1edf n\u00ean kh\u00f4ng th\u1ec3 th\u1ef1c hi\u1ec7n \u0111\u01b0\u1ee3c.<\/p>\n

    \n
  • Kh\u00f3a ch\u00ednh:<\/strong> M\u1ed9t c\u1ed9t ho\u1eb7c t\u1eadp h\u1ee3p c\u00e1c c\u1ed9t \u0111\u01b0\u1ee3c ch\u1ec9 \u0111\u1ecbnh l\u00e0 \u0111\u1ecbnh danh duy nh\u1ea5t cho m\u1ed9t b\u1ea3n ghi.<\/li>\n
  • Kh\u00f4ng \u0111\u01b0\u1ee3c \u0111\u1ec3 tr\u1ed1ng:<\/strong> C\u1ed9t kh\u00f3a ch\u00ednh kh\u00f4ng \u0111\u01b0\u1ee3c ch\u1ee9a gi\u00e1 tr\u1ecb null, \u0111\u1ea3m b\u1ea3o m\u1ecdi b\u1ea3n ghi \u0111\u1ec1u t\u1ed3n t\u1ea1i.<\/li>\n
  • T\u00ednh duy nh\u1ea5t:<\/strong> Kh\u00f4ng c\u00f3 hai h\u00e0ng n\u00e0o \u0111\u01b0\u1ee3c chia s\u1ebb c\u00f9ng m\u1ed9t gi\u00e1 tr\u1ecb kh\u00f3a ch\u00ednh.<\/li>\n<\/ul>\n

    2. To\u00e0n v\u1eb9n mi\u1ec1n<\/h3>\n

    To\u00e0n v\u1eb9n mi\u1ec1n h\u1ea1n ch\u1ebf c\u00e1c gi\u00e1 tr\u1ecb c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c \u0111\u1eb7t v\u00e0o m\u1ed9t c\u1ed9t c\u1ee5 th\u1ec3. \u0110i\u1ec1u n\u00e0y \u0111\u1ea3m b\u1ea3o d\u1eef li\u1ec7u lu\u00f4n n\u1eb1m trong c\u00e1c tham s\u1ed1 mong \u0111\u1ee3i, ch\u1eb3ng h\u1ea1n nh\u01b0 ki\u1ec3u d\u1eef li\u1ec7u, ph\u1ea1m vi ho\u1eb7c \u0111\u1ecbnh d\u1ea1ng.<\/p>\n

      \n
    • Ki\u1ec3u d\u1eef li\u1ec7u:<\/strong> \u0110\u1ea3m b\u1ea3o c\u1ed9t tu\u1ed5i ch\u1ec9 l\u01b0u tr\u1eef s\u1ed1 nguy\u00ean, kh\u00f4ng ph\u1ea3i v\u0103n b\u1ea3n.<\/li>\n
    • R\u00e0ng bu\u1ed9c ki\u1ec3m tra:<\/strong> X\u00e1c minh r\u1eb1ng m\u1ed9t gi\u00e1 tr\u1ecb n\u1eb1m trong ph\u1ea1m vi c\u1ee5 th\u1ec3, v\u00ed d\u1ee5 nh\u01b0 m\u1ed9t ph\u1ea7n tr\u0103m n\u1eb1m trong kho\u1ea3ng t\u1eeb 0 \u0111\u1ebfn 100.<\/li>\n
    • Gi\u00e1 tr\u1ecb m\u1eb7c \u0111\u1ecbnh:<\/strong> Cung c\u1ea5p gi\u00e1 tr\u1ecb thay th\u1ebf n\u1ebfu kh\u00f4ng c\u00f3 gi\u00e1 tr\u1ecb n\u00e0o \u0111\u01b0\u1ee3c cung c\u1ea5p trong qu\u00e1 tr\u00ecnh ch\u00e8n.<\/li>\n<\/ul>\n

      3. To\u00e0n v\u1eb9n tham chi\u1ebfu<\/h3>\n

      \u0110i\u1ec1u n\u00e0y \u0111\u1ea3m b\u1ea3o c\u00e1c m\u1ed1i quan h\u1ec7 gi\u1eefa c\u00e1c b\u1ea3ng lu\u00f4n nh\u1ea5t qu\u00e1n. N\u1ebfu m\u1ed9t b\u1ea3n ghi trong m\u1ed9t b\u1ea3ng tr\u1ecf \u0111\u1ebfn b\u1ea3n ghi kh\u00e1c, b\u1ea3n ghi \u0111\u00edch ph\u1ea3i t\u1ed3n t\u1ea1i. \u0110i\u1ec1u n\u00e0y ng\u0103n ng\u1eeba c\u00e1c b\u1ea3n ghi b\u1ecb b\u1ecf r\u01a1i, tr\u1ecf \u0111\u1ebfn d\u1eef li\u1ec7u kh\u00f4ng t\u1ed3n t\u1ea1i.<\/p>\n

        \n
      • Kh\u00f3a ngo\u1ea1i:<\/strong> M\u1ed9t c\u1ed9t li\u00ean k\u1ebft \u0111\u1ebfn kh\u00f3a ch\u00ednh c\u1ee7a b\u1ea3ng kh\u00e1c.<\/li>\n
      • Quy t\u1eafc lan truy\u1ec1n:<\/strong> X\u00e1c \u0111\u1ecbnh c\u00e1c h\u00e0nh \u0111\u1ed9ng (x\u00f3a ho\u1eb7c c\u1eadp nh\u1eadt) khi b\u1ea3n ghi cha thay \u0111\u1ed5i.<\/li>\n
      • X\u1eed l\u00fd gi\u00e1 tr\u1ecb null:<\/strong> Quy\u1ebft \u0111\u1ecbnh xem m\u1ed1i quan h\u1ec7 c\u00f3 th\u1ec3 t\u00f9y ch\u1ecdn (null) hay b\u1eaft bu\u1ed9c.<\/li>\n<\/ul>\n

        4. To\u00e0n v\u1eb9n do ng\u01b0\u1eddi d\u00f9ng \u0111\u1ecbnh ngh\u0129a<\/h3>\n

        \u0110\u00e2y l\u00e0 c\u00e1c quy t\u1eafc c\u1ee5 th\u1ec3 v\u1ec1 kinh doanh kh\u00f4ng ph\u00f9 h\u1ee3p v\u1edbi c\u00e1c danh m\u1ee5c ti\u00eau chu\u1ea9n. Ch\u00fang th\u01b0\u1eddng y\u00eau c\u1ea7u logic t\u00f9y ch\u1ec9nh trong l\u1edbp thi\u1ebft k\u1ebf ho\u1eb7c l\u1edbp \u1ee9ng d\u1ee5ng.<\/p>\n

          \n
        • X\u00e1c th\u1ef1c t\u00f9y ch\u1ec9nh:<\/strong>\u0110\u1ea3m b\u1ea3o ng\u00e0y th\u00e1ng kh\u00f4ng n\u1eb1m trong t\u01b0\u01a1ng lai.<\/li>\n
        • Logic \u0111i\u1ec1u ki\u1ec7n:<\/strong> N\u1ebfu tr\u1ea1ng th\u00e1i l\u00e0 \u201c\u0110\u00e3 h\u1ee7y,\u201d th\u00ec kh\u00f4ng \u0111\u01b0\u1ee3c ph\u00e9p c\u00f3 h\u1ed3 s\u01a1 thanh to\u00e1n n\u00e0o kh\u00e1c.<\/li>\n<\/ul>\n

          C\u00e1c r\u00e0ng bu\u1ed9c ERD c\u1ed1t l\u00f5i v\u00e0 t\u00e1c \u0111\u1ed9ng c\u1ee7a ch\u00fang \ud83e\uddf1<\/h2>\n

          ERD tr\u1ef1c quan h\u00f3a c\u00e1c r\u00e0ng bu\u1ed9c n\u00e0y, gi\u00fap c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n v\u00e0 b\u00ean li\u00ean quan c\u00f3 th\u1ec3 nh\u00ecn th\u1ea5y. B\u1ea3ng sau \u0111\u00e2y n\u00eau r\u00f5 c\u00e1c r\u00e0ng bu\u1ed9c ph\u1ed5 bi\u1ebfn, m\u1ee5c \u0111\u00edch c\u1ee7a ch\u00fang v\u00e0 t\u00e1c \u0111\u1ed9ng \u0111\u1ebfn t\u00ednh nh\u1ea5t qu\u00e1n c\u1ee7a d\u1eef li\u1ec7u.<\/p>\n\n\n\n\n\n\n\n\n\n
          Lo\u1ea1i r\u00e0ng bu\u1ed9c<\/th>\nCh\u1ee9c n\u0103ng<\/th>\n\u0110i\u1ec3m th\u1ef1c thi<\/th>\n<\/tr>\n<\/thead>\n
          Kh\u00f3a ch\u00ednh<\/td>\nX\u00e1c \u0111\u1ecbnh duy nh\u1ea5t c\u00e1c h\u00e0ng<\/td>\n\u0110\u1ecbnh ngh\u0129a b\u1ea3ng<\/td>\n<\/tr>\n
          Kh\u00f3a ngo\u1ea1i<\/td>\nLi\u00ean k\u1ebft c\u00e1c b\u1ea3ng v\u1edbi nhau<\/td>\n\u0110\u01b0\u1eddng m\u1ed1i quan h\u1ec7<\/td>\n<\/tr>\n
          Duy nh\u1ea5t<\/td>\nNg\u0103n ch\u1eb7n c\u00e1c gi\u00e1 tr\u1ecb tr\u00f9ng l\u1eb7p trong m\u1ed9t c\u1ed9t<\/td>\n\u0110\u1ecbnh ngh\u0129a c\u1ed9t<\/td>\n<\/tr>\n
          Kh\u00f4ng \u0111\u01b0\u1ee3c \u0111\u1ec3 tr\u1ed1ng<\/td>\nY\u00eau c\u1ea7u c\u00f3 gi\u00e1 tr\u1ecb cho tr\u01b0\u1eddng<\/td>\n\u0110\u1ecbnh ngh\u0129a c\u1ed9t<\/td>\n<\/tr>\n
          Ki\u1ec3m tra<\/td>\nX\u00e1c th\u1ef1c gi\u00e1 tr\u1ecb d\u1ef1a tr\u00ean m\u1ed9t \u0111i\u1ec1u ki\u1ec7n<\/td>\n\u0110\u1ecbnh ngh\u0129a c\u1ed9t ho\u1eb7c \u0111\u1ecbnh ngh\u0129a b\u1ea3ng<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

          Khi c\u00e1c r\u00e0ng bu\u1ed9c n\u00e0y \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh \u0111\u00fang c\u00e1ch trong thi\u1ebft k\u1ebf, b\u1ed9 \u0111\u1ed9ng c\u01a1 c\u01a1 s\u1edf d\u1eef li\u1ec7u n\u1ec1n t\u1ea3ng s\u1ebd t\u1ef1 \u0111\u1ed9ng th\u1ef1c thi ch\u00fang. \u0110i\u1ec1u n\u00e0y lo\u1ea1i b\u1ecf g\u00e1nh n\u1eb7ng x\u00e1c th\u1ef1c kh\u1ecfi m\u00e3 \u1ee9ng d\u1ee5ng, gi\u1ea3m thi\u1ec3u r\u1ee7i ro l\u1ed7i v\u00e0 l\u1ed7 h\u1ed5ng b\u1ea3o m\u1eadt.<\/p>\n

          \u0110\u1ed9 cardinality m\u1ed1i quan h\u1ec7 v\u00e0 t\u00ednh to\u00e0n v\u1eb9n \ud83d\udd04<\/h2>\n

          C\u00e1c \u0111\u01b0\u1eddng n\u1ed1i c\u00e1c th\u1ef1c th\u1ec3 trong ERD \u0111\u1ea1i di\u1ec7n cho c\u00e1c m\u1ed1i quan h\u1ec7. \u0110\u1ed9 cardinality c\u1ee7a c\u00e1c m\u1ed1i quan h\u1ec7 n\u00e0y x\u00e1c \u0111\u1ecbnh m\u1ee9c \u0111\u1ed9 nghi\u00eam ng\u1eb7t c\u1ee7a c\u00e1c quy t\u1eafc to\u00e0n v\u1eb9n c\u1ea7n thi\u1ebft.<\/p>\n

          C\u00e1c m\u1ed1i quan h\u1ec7 m\u1ed9t-m\u1ed9t<\/h3>\n

          \u0110i\u1ec1u n\u00e0y x\u1ea3y ra khi m\u1ed9t b\u1ea3n ghi trong B\u1ea3ng A kh\u1edbp ch\u00ednh x\u00e1c v\u1edbi m\u1ed9t b\u1ea3n ghi trong B\u1ea3ng B. \u0110\u00e2y l\u00e0 c\u00e1ch ph\u1ed5 bi\u1ebfn \u0111\u1ec3 chia nh\u1ecf c\u00e1c b\u1ea3ng l\u1edbn nh\u1eb1m m\u1ee5c \u0111\u00edch b\u1ea3o m\u1eadt ho\u1eb7c hi\u1ec7u su\u1ea5t.<\/p>\n

            \n
          • R\u00e0ng bu\u1ed9c:<\/strong>C\u1ea3 hai b\u00ean th\u01b0\u1eddng \u00e1p d\u1ee5ng t\u00ednh duy nh\u1ea5t cho kh\u00f3a ngo\u1ea1i.<\/li>\n
          • V\u00ed d\u1ee5:<\/strong>M\u1ed9t ng\u01b0\u1eddi v\u00e0 gi\u1ea5y t\u1edd t\u00f9y th\u00e2n c\u1ee7a h\u1ecd. M\u1ed9t ng\u01b0\u1eddi c\u00f3 m\u1ed9t gi\u1ea5y t\u1edd t\u00f9y th\u00e2n; m\u1ed9t gi\u1ea5y t\u1edd t\u00f9y th\u00e2n thu\u1ed9c v\u1ec1 m\u1ed9t ng\u01b0\u1eddi.<\/li>\n<\/ul>\n

            M\u1ed1i quan h\u1ec7 m\u1ed9t-\u0111a<\/h3>\n

            Lo\u1ea1i m\u1ed1i quan h\u1ec7 ph\u1ed5 bi\u1ebfn nh\u1ea5t. M\u1ed9t b\u1ea3n ghi trong B\u1ea3ng A c\u00f3 th\u1ec3 li\u00ean k\u1ebft v\u1edbi nhi\u1ec1u b\u1ea3n ghi trong B\u1ea3ng B.<\/p>\n

              \n
            • R\u00e0ng bu\u1ed9c:<\/strong>Kh\u00f3a ngo\u1ea1i n\u1eb1m trong b\u1ea3ng \u1edf ph\u00eda ‘nhi\u1ec1u’ b\u00ean.<\/li>\n
            • To\u00e0n v\u1eb9n:<\/strong>Kh\u00f3a ngo\u1ea1i ph\u1ea3i tham chi\u1ebfu \u0111\u1ebfn kh\u00f3a ch\u00ednh t\u1ed3n t\u1ea1i trong b\u1ea3ng \u1edf ph\u00eda ‘m\u1ed9t’ b\u00ean.<\/li>\n
            • V\u00ed d\u1ee5:<\/strong>M\u1ed9t kh\u00e1ch h\u00e0ng v\u00e0 c\u00e1c \u0111\u01a1n \u0111\u1eb7t h\u00e0ng c\u1ee7a h\u1ecd. M\u1ed9t kh\u00e1ch h\u00e0ng c\u00f3 nhi\u1ec1u \u0111\u01a1n \u0111\u1eb7t h\u00e0ng; m\u1ed9t \u0111\u01a1n \u0111\u1eb7t h\u00e0ng thu\u1ed9c v\u1ec1 m\u1ed9t kh\u00e1ch h\u00e0ng.<\/li>\n<\/ul>\n

              M\u1ed1i quan h\u1ec7 \u0111a-\u0111a<\/h3>\n

              \u0110i\u1ec1u n\u00e0y y\u00eau c\u1ea7u m\u1ed9t b\u1ea3ng li\u00ean k\u1ebft \u0111\u1ec3 gi\u1ea3i quy\u1ebft m\u1ed1i quan h\u1ec7 th\u00e0nh hai k\u1ebft n\u1ed1i m\u1ed9t-\u0111a.<\/p>\n

                \n
              • R\u00e0ng bu\u1ed9c:<\/strong>B\u1ea3ng li\u00ean k\u1ebft ch\u1ee9a kh\u00f3a ch\u00ednh h\u1ee3p th\u00e0nh ho\u1eb7c r\u00e0ng bu\u1ed9c duy nh\u1ea5t \u0111\u1ec3 ng\u0103n ch\u1eb7n c\u00e1c li\u00ean k\u1ebft tr\u00f9ng l\u1eb7p.<\/li>\n
              • To\u00e0n v\u1eb9n:<\/strong>Ng\u0103n ch\u1eb7n d\u1eef li\u1ec7u v\u00f2ng l\u1eb7p ho\u1eb7c c\u00e1c m\u1ee5c nh\u1eadp d\u01b0 th\u1eeba trong b\u1ea3ng li\u00ean k\u1ebft.<\/li>\n
              • V\u00ed d\u1ee5:<\/strong>Sinh vi\u00ean v\u00e0 c\u00e1c kh\u00f3a h\u1ecdc. M\u1ed9t sinh vi\u00ean tham gia nhi\u1ec1u kh\u00f3a h\u1ecdc; m\u1ed9t kh\u00f3a h\u1ecdc c\u00f3 nhi\u1ec1u sinh vi\u00ean.<\/li>\n<\/ul>\n

                Chu\u1ea9n h\u00f3a v\u00e0 t\u00ednh nh\u1ea5t qu\u00e1n d\u1eef li\u1ec7u \ud83d\udcd0<\/h2>\n

                Chu\u1ea9n h\u00f3a l\u00e0 qu\u00e1 tr\u00ecnh t\u1ed5 ch\u1ee9c d\u1eef li\u1ec7u \u0111\u1ec3 gi\u1ea3m thi\u1ec3u s\u1ef1 tr\u00f9ng l\u1eb7p v\u00e0 c\u1ea3i thi\u1ec7n t\u00ednh to\u00e0n v\u1eb9n. M\u1eb7c d\u00f9 th\u01b0\u1eddng \u0111\u01b0\u1ee3c xem nh\u01b0 m\u1ed9t bi\u1ec7n ph\u00e1p t\u1ed1i \u01b0u hi\u1ec7u su\u1ea5t, nh\u01b0ng n\u00f3 ch\u1ee7 y\u1ebfu l\u00e0 m\u1ed9t chi\u1ebfn l\u01b0\u1ee3c \u0111\u1ea3m b\u1ea3o t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u.<\/p>\n

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

                \u0110\u1ea3m b\u1ea3o r\u1eb1ng m\u1ed7i c\u1ed9t ch\u1ee9a c\u00e1c gi\u00e1 tr\u1ecb nguy\u00ean t\u1eed. Kh\u00f4ng c\u00f3 danh s\u00e1ch hay m\u1ea3ng trong m\u1ed9t \u00f4 duy nh\u1ea5t.<\/p>\n

                  \n
                • L\u1ee3i \u00edch:<\/strong>\u0110\u01a1n gi\u1ea3n h\u00f3a truy v\u1ea5n v\u00e0 \u0111\u1ea3m b\u1ea3o ki\u1ec3u d\u1eef li\u1ec7u nh\u1ea5t qu\u00e1n.<\/li>\n
                • R\u1ee7i ro vi ph\u1ea1m:<\/strong>L\u01b0u tr\u1eef nhi\u1ec1u s\u1ed1 \u0111i\u1ec7n tho\u1ea1i trong m\u1ed9t tr\u01b0\u1eddng khi\u1ebfn vi\u1ec7c c\u1eadp nh\u1eadt m\u1ed9t s\u1ed1 \u0111\u01a1n l\u1ebb tr\u1edf n\u00ean kh\u00f3 kh\u0103n.<\/li>\n<\/ul>\n

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

                  Y\u00eau c\u1ea7u b\u1ea3ng ph\u1ea3i \u1edf d\u1ea1ng 1NF v\u00e0 t\u1ea5t c\u1ea3 c\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng kh\u00f3a ph\u1ea3i ph\u1ee5 thu\u1ed9c ho\u00e0n to\u00e0n v\u00e0o kh\u00f3a ch\u00ednh.<\/p>\n

                    \n
                  • L\u1ee3i \u00edch:<\/strong>Lo\u1ea1i b\u1ecf c\u00e1c ph\u1ee5 thu\u1ed9c ri\u00eang ph\u1ea7n.<\/li>\n
                  • R\u1ee7i ro vi ph\u1ea1m:<\/strong>L\u01b0u tr\u1eef chi ti\u1ebft \u0111\u1ecba ch\u1ec9 kh\u00e1ch h\u00e0ng trong b\u1ea3ng \u0110\u01a1n h\u00e0ng s\u1ebd t\u1ea1o ra s\u1ef1 tr\u00f9ng l\u1eb7p n\u1ebfu kh\u00e1ch h\u00e0ng chuy\u1ec3n \u0111\u1ecba ch\u1ec9.<\/li>\n<\/ul>\n

                    D\u1ea1ng chu\u1ea9n h\u00f3a th\u1ee9 ba (3NF)<\/h3>\n

                    Y\u00eau c\u1ea7u b\u1ea3ng ph\u1ea3i \u1edf d\u1ea1ng chu\u1ea9n h\u00f3a th\u1ee9 hai (2NF) v\u00e0 kh\u00f4ng c\u00f3 c\u00e1c ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u.<\/p>\n

                      \n
                    • L\u1ee3i \u00edch:<\/strong>\u0110\u1ea3m b\u1ea3o c\u00e1c thu\u1ed9c t\u00ednh ch\u1ec9 ph\u1ee5 thu\u1ed9c v\u00e0o kh\u00f3a ch\u00ednh.<\/li>\n
                    • R\u1ee7i ro vi ph\u1ea1m:<\/strong>L\u01b0u t\u00ean th\u00e0nh ph\u1ed1 trong b\u1ea3ng kh\u00e1ch h\u00e0ng khi th\u00e0nh ph\u1ed1 \u0111\u00f3 \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh b\u1edfi m\u00e3 b\u01b0u ch\u00ednh (m\u00e3 b\u01b0u ch\u00ednh x\u00e1c \u0111\u1ecbnh th\u00e0nh ph\u1ed1) s\u1ebd t\u1ea1o ra c\u00e1c b\u1ea5t th\u01b0\u1eddng khi c\u1eadp nh\u1eadt.<\/li>\n<\/ul>\n

                      Chi\u1ebfn l\u01b0\u1ee3c tri\u1ec3n khai cho thi\u1ebft k\u1ebf b\u1ec1n v\u1eefng \ud83d\udee0\ufe0f<\/h2>\n

                      \u00c1p d\u1ee5ng c\u00e1c kh\u00e1i ni\u1ec7m n\u00e0y \u0111\u00f2i h\u1ecfi c\u00e1ch ti\u1ebfp c\u1eadn c\u00f3 k\u1ef7 lu\u1eadt trong giai \u0111o\u1ea1n m\u00f4 h\u00ecnh h\u00f3a. C\u00e1c chi\u1ebfn l\u01b0\u1ee3c sau \u0111\u00e2y gi\u00fap duy tr\u00ec c\u00e1c ti\u00eau chu\u1ea9n to\u00e0n v\u1eb9n cao.<\/p>\n

                        \n
                      • Quy \u01b0\u1edbc \u0111\u1eb7t t\u00ean r\u00f5 r\u00e0ng:<\/strong>S\u1eed d\u1ee5ng t\u00ean r\u00f5 r\u00e0ng cho c\u00e1c kh\u00f3a ngo\u1ea1i (v\u00ed d\u1ee5: user_id<\/code>thay v\u00ec fk1<\/code>) \u0111\u1ec3 l\u00e0m r\u00f5 m\u1ed1i quan h\u1ec7 trong qu\u00e1 tr\u00ecnh ki\u1ec3m tra m\u00e3 ngu\u1ed3n.<\/li>\n
                      • T\u00e0i li\u1ec7u:<\/strong>Ghi ch\u00fa c\u00e1c quy t\u1eafc kinh doanh l\u00ean s\u01a1 \u0111\u1ed3 ERD. M\u1ed9t r\u00e0ng bu\u1ed9c m\u00e0 kh\u00f4ng c\u00f3 ng\u1eef c\u1ea3nh s\u1ebd kh\u00f3 duy tr\u00ec.<\/li>\n
                      • X\u00e1c minh tr\u01b0\u1edbc khi t\u1ea1o:<\/strong>Xem x\u00e9t thi\u1ebft k\u1ebf \u0111\u1ec3 ph\u00e1t hi\u1ec7n c\u00e1c b\u1ea3n ghi b\u1ecb t\u00e1ch r\u1eddi ti\u1ec1m \u1ea9n tr\u01b0\u1edbc khi di chuy\u1ec3n c\u1ea5u tr\u00fac c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/li>\n
                      • T\u1ea1m th\u1eddi v\u00f4 hi\u1ec7u h\u00f3a r\u00e0ng bu\u1ed9c:<\/strong>Ch\u1ec9 v\u00f4 hi\u1ec7u h\u00f3a ki\u1ec3m tra to\u00e0n v\u1eb9n trong qu\u00e1 tr\u00ecnh t\u1ea3i d\u1eef li\u1ec7u h\u00e0ng lo\u1ea1t, v\u00e0 kh\u00f4i ph\u1ee5c l\u1ea1i ngay l\u1eadp t\u1ee9c sau \u0111\u00f3 \u0111\u1ec3 x\u00e1c minh ch\u1ea5t l\u01b0\u1ee3ng d\u1eef li\u1ec7u.<\/li>\n
                      • D\u00f2ng nh\u1eadt k\u00fd ki\u1ec3m to\u00e1n:<\/strong>Ghi l\u1ea1i c\u00e1c thay \u0111\u1ed5i v\u00e0o c\u00e1c tr\u01b0\u1eddng to\u00e0n v\u1eb9n quan tr\u1ecdng \u0111\u1ec3 theo d\u00f5i ai \u0111\u00e3 thay \u0111\u1ed5i d\u1eef li\u1ec7u v\u00e0 khi n\u00e0o.<\/li>\n<\/ul>\n

                        Nh\u1eefng sai l\u1ea7m ph\u1ed5 bi\u1ebfn trong qu\u1ea3n l\u00fd r\u00e0ng bu\u1ed9c \u26a0\ufe0f<\/h2>\n

                        Ngay c\u1ea3 v\u1edbi k\u1ebf ho\u1ea1ch v\u1eefng ch\u1eafc, l\u1ed7i v\u1eabn x\u1ea3y ra. Nh\u1eadn di\u1ec7n nh\u1eefng sai l\u1ea7m ph\u1ed5 bi\u1ebfn s\u1ebd gi\u00fap tr\u00e1nh \u0111\u01b0\u1ee3c ch\u00fang.<\/p>\n

                        1. C\u00e1c ph\u1ee5 thu\u1ed9c v\u00f2ng tr\u00f2n<\/h3>\n

                        T\u1ea1o ra t\u00ecnh hu\u1ed1ng m\u00e0 B\u1ea3ng A ph\u1ee5 thu\u1ed9c v\u00e0o B\u1ea3ng B, v\u00e0 B\u1ea3ng B ph\u1ee5 thu\u1ed9c v\u00e0o B\u1ea3ng A. \u0110i\u1ec1u n\u00e0y d\u1eabn \u0111\u1ebfn k\u1eb9t h\u00e0ng trong qu\u00e1 tr\u00ecnh t\u1ea1o b\u1ea3ng.<\/p>\n

                          \n
                        • Gi\u1ea3i ph\u00e1p:<\/strong>T\u1ea1o c\u00e1c b\u1ea3ng m\u00e0 kh\u00f4ng c\u00f3 r\u00e0ng bu\u1ed9c kh\u00f3a ngo\u1ea1i tr\u01b0\u1edbc, sau \u0111\u00f3 th\u00eam r\u00e0ng bu\u1ed9c n\u00e0y sau khi c\u1ea3 hai b\u1ea3ng \u0111\u1ec1u t\u1ed3n t\u1ea1i.<\/li>\n<\/ul>\n

                          2. C\u01b0\u1ee1ng ch\u1ebf qu\u00e1 m\u1ee9c<\/h3>\n

                          \u00c1p d\u1ee5ng c\u00e1c r\u00e0ng bu\u1ed9c nghi\u00eam ng\u1eb7t \u1edf nh\u1eefng n\u01a1i c\u1ea7n s\u1ef1 linh ho\u1ea1t. \u0110i\u1ec1u n\u00e0y c\u00f3 th\u1ec3 l\u00e0m c\u1ea3n tr\u1edf c\u00e1c ho\u1ea1t \u0111\u1ed9ng kinh doanh h\u1ee3p ph\u00e1p.<\/p>\n

                            \n
                          • Gi\u1ea3i ph\u00e1p:<\/strong>S\u1eed d\u1ee5ng kh\u00f3a ngo\u1ea1i c\u00f3 th\u1ec3 null cho c\u00e1c m\u1ed1i quan h\u1ec7 t\u00f9y ch\u1ecdn v\u00e0 x\u1eed l\u00fd x\u00e1c th\u1ef1c \u1edf l\u1edbp \u1ee9ng d\u1ee5ng n\u1ebfu c\u1ea7n logic ph\u1ee9c t\u1ea1p.<\/li>\n<\/ul>\n

                            3. B\u1ecf qua x\u00f3a m\u1ec1m<\/h3>\n

                            S\u1eed d\u1ee5ng m\u1ed9t X\u00d3A<\/code>L\u1ec7nh X\u00d3A x\u00f3a d\u1eef li\u1ec7u v\u0129nh vi\u1ec5n, l\u00e0m h\u1ecfng t\u00ednh to\u00e0n v\u1eb9n tham chi\u1ebfu \u0111\u1ed1i v\u1edbi c\u00e1c b\u1ea3n ghi l\u1ecbch s\u1eed.<\/p>\n

                              \n
                            • Gi\u1ea3i ph\u00e1p:<\/strong>Th\u1ef1c hi\u1ec7n m\u1ed9t is_deleted<\/code>c\u1edd ki\u1ec3u boolean thay v\u00ec x\u00f3a v\u1eadt l\u00fd cho d\u1eef li\u1ec7u l\u1ecbch s\u1eed quan tr\u1ecdng.<\/li>\n<\/ul>\n

                              4. S\u1ef1 \u0111\u00e1nh \u0111\u1ed5i gi\u1eefa hi\u1ec7u su\u1ea5t v\u00e0 to\u00e0n v\u1eb9n<\/h3>\n

                              C\u00e1c r\u00e0ng bu\u1ed9c qu\u00e1 m\u1ee9c c\u00f3 th\u1ec3 l\u00e0m ch\u1eadm c\u00e1c thao t\u00e1c ghi. M\u1ed7i thao t\u00e1c ch\u00e8n ph\u1ea3i ki\u1ec3m tra t\u1eebng quy t\u1eafc.<\/p>\n

                                \n
                              • Gi\u1ea3i ph\u00e1p:<\/strong>Ch\u1ec9 m\u1ee5c c\u00e1c kh\u00f3a ngo\u1ea1i \u0111\u1ec3 t\u0103ng t\u1ed1c t\u00ecm ki\u1ebfm. C\u00e2n b\u1eb1ng nhu c\u1ea7u x\u00e1c th\u1ef1c th\u1eddi gian th\u1ef1c v\u1edbi y\u00eau c\u1ea7u v\u1ec1 b\u0103ng th\u00f4ng h\u1ec7 th\u1ed1ng.<\/li>\n<\/ul>\n

                                Duy tr\u00ec to\u00e0n v\u1eb9n theo th\u1eddi gian \ud83d\udd04<\/h2>\n

                                To\u00e0n v\u1eb9n d\u1eef li\u1ec7u kh\u00f4ng ph\u1ea3i l\u00e0 thi\u1ebft l\u1eadp m\u1ed9t l\u1ea7n. Khi y\u00eau c\u1ea7u kinh doanh thay \u0111\u1ed5i, l\u01b0\u1ee3c \u0111\u1ed3 ph\u1ea3i th\u00edch nghi m\u00e0 kh\u00f4ng l\u00e0m t\u1ed5n h\u1ea1i \u0111\u1ebfn d\u1eef li\u1ec7u hi\u1ec7n c\u00f3.<\/p>\n

                                  \n
                                • Phi\u00ean b\u1ea3n l\u01b0\u1ee3c \u0111\u1ed3:<\/strong>Xem c\u00e1c thay \u0111\u1ed5i c\u01a1 s\u1edf d\u1eef li\u1ec7u nh\u01b0 m\u00e3 ngu\u1ed3n. Ki\u1ec3m so\u00e1t phi\u00ean b\u1ea3n cho ph\u00e9p ho\u00e0n nguy\u00ean n\u1ebfu m\u1ed9t r\u00e0ng bu\u1ed9c l\u00e0m h\u1ecfng h\u1ec7 th\u1ed1ng.<\/li>\n
                                • Ki\u1ec3m th\u1eed di chuy\u1ec3n:<\/strong>Ch\u1ea1y c\u00e1c k\u1ecbch b\u1ea3n di chuy\u1ec3n trong m\u00f4i tr\u01b0\u1eddng th\u1eed nghi\u1ec7m m\u00f4 ph\u1ecfng dung l\u01b0\u1ee3ng d\u1eef li\u1ec7u s\u1ea3n xu\u1ea5t.<\/li>\n
                                • Ki\u1ec3m to\u00e1n \u0111\u1ecbnh k\u1ef3:<\/strong>Ch\u1ea1y c\u00e1c truy v\u1ea5n \u0111\u1ec3 t\u00ecm c\u00e1c b\u1ea3n ghi b\u1ecb b\u1ecf r\u01a1i c\u00f3 th\u1ec3 \u0111\u00e3 l\u1ecdt qua do l\u1ed7i ph\u1ea7n m\u1ec1m ho\u1eb7c truy c\u1eadp tr\u1ef1c ti\u1ebfp.<\/li>\n
                                • Chi\u1ebfn l\u01b0\u1ee3c sao l\u01b0u:<\/strong>Sao l\u01b0u \u0111\u1ecbnh k\u1ef3 \u0111\u1ea3m b\u1ea3o r\u1eb1ng n\u1ebfu to\u00e0n v\u1eb9n b\u1ecb vi ph\u1ea1m, tr\u1ea1ng th\u00e1i s\u1ea1ch s\u1ebd s\u1ebd s\u1eb5n s\u00e0ng \u0111\u1ec3 ph\u1ee5c h\u1ed3i.<\/li>\n<\/ul>\n

                                  Suy ngh\u0129 cu\u1ed1i c\u00f9ng v\u1ec1 s\u1ef1 nghi\u00eam ng\u1eb7t c\u1ea5u tr\u00fac \ud83c\udfaf<\/h2>\n

                                  X\u00e2y d\u1ef1ng m\u1ed9t h\u1ec7 th\u1ed1ng v\u1edbi to\u00e0n v\u1eb9n d\u1eef li\u1ec7u m\u1ea1nh m\u1ebd \u0111\u00f2i h\u1ecfi t\u1ea7m nh\u00ecn v\u00e0 k\u1ef7 lu\u1eadt. S\u01a1 \u0111\u1ed3 ERD \u0111\u00f3ng vai tr\u00f2 l\u00e0 c\u00f4ng c\u1ee5 ch\u00ednh \u0111\u1ec3 truy\u1ec1n \u0111\u1ea1t c\u00e1c quy t\u1eafc n\u00e0y \u0111\u1ebfn to\u00e0n b\u1ed9 \u0111\u1ed9i ng\u0169 ph\u00e1t tri\u1ec3n. B\u1eb1ng c\u00e1ch th\u1ef1c thi c\u00e1c r\u00e0ng bu\u1ed9c \u1edf c\u1ea5p \u0111\u1ed9 c\u01a1 s\u1edf d\u1eef li\u1ec7u, c\u00e1c t\u1ed5 ch\u1ee9c gi\u1ea3m thi\u1ec3u \u0111\u1ed9 ph\u1ee9c t\u1ea1p c\u1ee7a logic \u1ee9ng d\u1ee5ng v\u00e0 t\u0103ng s\u1ef1 tin t\u01b0\u1edfng v\u00e0o d\u1eef li\u1ec7u c\u1ee7a m\u00ecnh.<\/p>\n

                                  M\u1ed7i r\u00e0ng bu\u1ed9c \u0111\u01b0\u1ee3c th\u00eam v\u00e0o \u0111\u1ec1u l\u00e0 m\u1ed9t r\u00e0o ch\u1eafn an to\u00e0n. Ch\u00fang ng\u0103n h\u1ec7 th\u1ed1ng l\u1ec7ch kh\u1ecfi qu\u1ef9 \u0111\u1ea1o. M\u1eb7c d\u00f9 ch\u00fang c\u00f3 th\u1ec3 tr\u00f4ng h\u1ea1n ch\u1ebf trong giai \u0111o\u1ea1n thi\u1ebft k\u1ebf, nh\u01b0ng ch\u00fang mang l\u1ea1i s\u1ef1 \u1ed5n \u0111\u1ecbnh c\u1ea7n thi\u1ebft cho s\u1ef1 ph\u00e1t tri\u1ec3n d\u00e0i h\u1ea1n. \u01afu ti\u00ean c\u00e1c quy t\u1eafc n\u00e0y \u0111\u1ea3m b\u1ea3o d\u1eef li\u1ec7u v\u1eabn l\u00e0 m\u1ed9t t\u00e0i s\u1ea3n \u0111\u00e1ng tin c\u1eady thay v\u00ec m\u1ed9t m\u1ed1i r\u1ee7i ro.<\/p>\n

                                  Vi\u1ec7c \u00e1p d\u1ee5ng c\u00e1c th\u1ef1c h\u00e0nh n\u00e0y t\u1ea1o ra m\u1ed9t ki\u1ebfn tr\u00fac linh ho\u1ea1t, c\u00f3 kh\u1ea3 n\u0103ng ch\u1ecbu \u0111\u1ef1ng \u0111\u01b0\u1ee3c s\u1ef1 ph\u1ee9c t\u1ea1p c\u1ee7a x\u1eed l\u00fd d\u1eef li\u1ec7u hi\u1ec7n \u0111\u1ea1i. K\u1ebft qu\u1ea3 l\u00e0 m\u1ed9t h\u1ec7 th\u1ed1ng m\u00e0 \u0111\u1ed9 ch\u00ednh x\u00e1c \u0111\u01b0\u1ee3c t\u00edch h\u1ee3p s\u1eb5n, ch\u1ee9 kh\u00f4ng ph\u1ea3i \u0111\u01b0\u1ee3c b\u1ed5 sung sau.<\/p>\n","protected":false},"excerpt":{"rendered":"

                                  Trong ki\u1ebfn tr\u00fac d\u1eef li\u1ec7u hi\u1ec7n \u0111\u1ea1i, \u0111\u1ed9 tin c\u1eady c\u1ee7a th\u00f4ng tin ph\u1ee5 thu\u1ed9c v\u00e0o c\u00e1c bi\u1ec7n ph\u00e1p b\u1ea3o v\u1ec7 c\u1ea5u tr\u00fac \u0111\u01b0\u1ee3c x\u00e2y d\u1ef1ng trong giai \u0111o\u1ea1n thi\u1ebft…<\/p>\n","protected":false},"author":1,"featured_media":1619,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_yoast_wpseo_title":"Th\u1ef1c thi t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u b\u1eb1ng c\u00e1c r\u00e0ng bu\u1ed9c ERD \ud83d\udee1\ufe0f","_yoast_wpseo_metadesc":"H\u1ecdc c\u00e1ch th\u1ef1c thi t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u th\u00f4ng qua c\u00e1c r\u00e0ng bu\u1ed9c ERD nghi\u00eam ng\u1eb7t. Kh\u00e1m ph\u00e1 PK, FK, chu\u1ea9n h\u00f3a v\u00e0 c\u00e1c th\u1ef1c h\u00e0nh t\u1ed1t nh\u1ea5t trong thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u \u0111\u1ec3 x\u00e2y d\u1ef1ng c\u00e1c h\u1ec7 th\u1ed1ng \u0111\u00e1ng tin c\u1eady.","fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[65],"tags":[80,84],"class_list":["post-1618","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-database-design","tag-academic","tag-erd"],"yoast_head":"\nTh\u1ef1c thi t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u b\u1eb1ng c\u00e1c r\u00e0ng bu\u1ed9c ERD \ud83d\udee1\ufe0f<\/title>\n<meta name=\"description\" content=\"H\u1ecdc c\u00e1ch th\u1ef1c thi t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u th\u00f4ng qua c\u00e1c r\u00e0ng bu\u1ed9c ERD nghi\u00eam ng\u1eb7t. 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