{"id":85,"date":"2026-04-03T03:29:02","date_gmt":"2026-04-03T03:29:02","guid":{"rendered":"https:\/\/www.we-notes.com\/vn\/normalization-denormalization-erd-guide\/"},"modified":"2026-04-03T03:29:02","modified_gmt":"2026-04-03T03:29:02","slug":"normalization-denormalization-erd-guide","status":"publish","type":"post","link":"https:\/\/www.we-notes.com\/vn\/normalization-denormalization-erd-guide\/","title":{"rendered":"C\u00e2u h\u1ecfi & C\u00e2u tr\u1ea3 l\u1eddi: Gi\u1ea3i quy\u1ebft nh\u1eefng c\u00e2u h\u1ecfi kh\u00f3 nh\u1ea5t v\u1ec1 Chu\u1ea9n h\u00f3a v\u00e0 Phi chu\u1ea9n h\u00f3a trong S\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3"},"content":{"rendered":"

Thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u l\u00e0 n\u1ec1n t\u1ea3ng c\u1ee7a b\u1ea5t k\u1ef3 \u1ee9ng d\u1ee5ng m\u1ea1nh m\u1ebd n\u00e0o. Khi x\u00e2y d\u1ef1ng S\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 (ERD), hai l\u1ef1c l\u01b0\u1ee3ng \u0111\u1ed1i l\u1eadp h\u00ecnh th\u00e0nh c\u1ea5u tr\u00fac: chu\u1ea9n h\u00f3a v\u00e0 phi chu\u1ea9n h\u00f3a. Hi\u1ec3u r\u00f5 khi n\u00e0o \u00e1p d\u1ee5ng chi\u1ebfn l\u01b0\u1ee3c n\u00e0o s\u1ebd quy\u1ebft \u0111\u1ecbnh s\u1ee9c kh\u1ecfe l\u00e2u d\u00e0i, hi\u1ec7u su\u1ea5t v\u00e0 kh\u1ea3 n\u0103ng b\u1ea3o tr\u00ec c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n. H\u01b0\u1edbng d\u1eabn n\u00e0y gi\u1ea3i quy\u1ebft nh\u1eefng c\u00e2u h\u1ecfi quan tr\u1ecdng nh\u1ea5t v\u1ec1 c\u00e1c kh\u00e1i ni\u1ec7m n\u00e0y, cung c\u1ea5p con \u0111\u01b0\u1eddng r\u00f5 r\u00e0ng \u0111\u1ec3 thi\u1ebft k\u1ebf c\u00e1c c\u1ea5u tr\u00fac c\u01a1 s\u1edf d\u1eef li\u1ec7u hi\u1ec7u qu\u1ea3 m\u00e0 kh\u00f4ng c\u1ea7n ph\u1ee5 thu\u1ed9c v\u00e0o c\u00f4ng c\u1ee5 ph\u1ea7n m\u1ec1m c\u1ee5 th\u1ec3. \ud83d\udee0\ufe0f<\/p>\n

T\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u v\u00e0 t\u1ed1c \u0111\u1ed9 truy v\u1ea5n th\u01b0\u1eddng k\u00e9o nhau theo hai h\u01b0\u1edbng \u0111\u1ed1i l\u1eadp. Chu\u1ea9n h\u00f3a \u01b0u ti\u00ean t\u00ednh to\u00e0n v\u1eb9n b\u1eb1ng c\u00e1ch gi\u1ea3m thi\u1ec3u s\u1ef1 tr\u00f9ng l\u1eb7p. Phi chu\u1ea9n h\u00f3a \u01b0u ti\u00ean t\u1ed1c \u0111\u1ed9 b\u1eb1ng c\u00e1ch gi\u1edbi thi\u1ec7u s\u1ef1 tr\u00f9ng l\u1eb7p \u0111\u01b0\u1ee3c ki\u1ec3m so\u00e1t. Vi\u1ec7c \u0111i\u1ec1u ch\u1ec9nh s\u1ef1 c\u00e2n b\u1eb1ng n\u00e0y \u0111\u00f2i h\u1ecfi hi\u1ec3u bi\u1ebft s\u00e2u s\u1eafc v\u1ec1 l\u00fd thuy\u1ebft quan h\u1ec7 v\u00e0 c\u00e1c y\u00eau c\u1ea7u th\u1ef1c ti\u1ec5n v\u1ec1 hi\u1ec7u su\u1ea5t. H\u00e3y c\u00f9ng kh\u00e1m ph\u00e1 c\u00e1c chi ti\u1ebft k\u1ef9 thu\u1eadt th\u00f4ng qua lo\u1ea1t c\u00e2u h\u1ecfi v\u00e0 c\u00e2u tr\u1ea3 l\u1eddi c\u1ee5 th\u1ec3. \ud83d\udcca<\/p>\n

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

Hi\u1ec3u r\u00f5 c\u00e1c n\u1ec1n t\u1ea3ng: Ch\u00fang ta \u0111ang \u0111\u1ed1i m\u1eb7t v\u1edbi \u0111i\u1ec1u g\u00ec? \ud83d\udd0d<\/h2>\n

Tr\u01b0\u1edbc khi \u0111i v\u00e0o c\u00e1c t\u00ecnh hu\u1ed1ng c\u1ee5 th\u1ec3, ch\u00fang ta c\u1ea7n x\u00e1c \u0111\u1ecbnh c\u00e1c c\u01a1 ch\u1ebf c\u1ed1t l\u00f5i \u0111ang ho\u1ea1t \u0111\u1ed9ng trong thi\u1ebft k\u1ebf ERD c\u1ee7a b\u1ea1n.<\/p>\n

Chu\u1ea9n h\u00f3a l\u00e0 g\u00ec? \ud83d\udd04<\/h3>\n

Chu\u1ea9n h\u00f3a l\u00e0 qu\u00e1 tr\u00ecnh c\u00f3 h\u1ec7 th\u1ed1ng t\u1ed5 ch\u1ee9c d\u1eef li\u1ec7u trong c\u01a1 s\u1edf 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 d\u1eef li\u1ec7u. 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 \u0111\u1ea3m b\u1ea3o m\u1ed7i ph\u1ea7n d\u1eef li\u1ec7u ch\u1ec9 \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef t\u1ea1i m\u1ed9t v\u1ecb tr\u00ed duy nh\u1ea5t.<\/p>\n

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  • M\u1ee5c ti\u00eau:<\/strong>Lo\u1ea1i b\u1ecf d\u1eef li\u1ec7u tr\u00f9ng l\u1eb7p v\u00e0 \u0111\u1ea3m b\u1ea3o c\u00e1c ph\u1ee5 thu\u1ed9c l\u00e0 h\u1ee3p l\u00fd.<\/li>\n
  • L\u1ee3i \u00edch:<\/strong>Gi\u1ea3m \u0111\u1ed9 ph\u1ee9c t\u1ea1p trong b\u1ea3o tr\u00ec d\u1eef li\u1ec7u v\u00e0 gi\u1ea3m y\u00eau c\u1ea7u l\u01b0u tr\u1eef.<\/li>\n
  • Chi ph\u00ed:<\/strong>L\u00e0m t\u0103ng \u0111\u1ed9 ph\u1ee9c t\u1ea1p c\u1ee7a truy v\u1ea5n do y\u00eau c\u1ea7u th\u1ef1c hi\u1ec7n c\u00e1c thao t\u00e1c n\u1ed1i b\u1ea3ng.<\/li>\n<\/ul>\n

    Chu\u1ea9n h\u00f3a th\u01b0\u1eddng \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n th\u00f4ng qua m\u1ed9t chu\u1ed7i c\u00e1c giai \u0111o\u1ea1n \u0111\u01b0\u1ee3c g\u1ecdi l\u00e0 C\u00e1c d\u1ea1ng chu\u1ea9n. M\u1ed7i d\u1ea1ng x\u00e2y d\u1ef1ng tr\u00ean d\u1ea1ng tr\u01b0\u1edbc \u0111\u00f3, gi\u1ea3i quy\u1ebft c\u00e1c lo\u1ea1i hi\u1ec7n t\u01b0\u1ee3ng b\u1ea5t th\u01b0\u1eddng c\u1ee5 th\u1ec3.<\/p>\n

    Phi chu\u1ea9n h\u00f3a l\u00e0 g\u00ec? \u2696\ufe0f<\/h3>\n

    Phi chu\u1ea9n h\u00f3a l\u00e0 vi\u1ec7c ch\u1ee7 \u00fd \u0111\u01b0a s\u1ef1 tr\u00f9ng l\u1eb7p v\u00e0o c\u01a1 s\u1edf d\u1eef li\u1ec7u \u0111\u00e3 \u0111\u01b0\u1ee3c chu\u1ea9n h\u00f3a. Vi\u1ec7c n\u00e0y \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n \u0111\u1ec3 t\u1ed1i \u01b0u hi\u1ec7u su\u1ea5t \u0111\u1ecdc, \u0111\u1eb7c bi\u1ec7t trong c\u00e1c t\u00ecnh hu\u1ed1ng m\u00e0 t\u1ed1c \u0111\u1ed9 truy v\u1ea5n quan tr\u1ecdng h\u01a1n t\u1ed1c \u0111\u1ed9 ghi. N\u00f3 bao g\u1ed3m vi\u1ec7c g\u1ed9p c\u00e1c b\u1ea3ng ho\u1eb7c th\u00eam c\u00e1c c\u1ed9t tr\u00f9ng l\u1eb7p \u0111\u1ec3 tr\u00e1nh c\u00e1c thao t\u00e1c n\u1ed1i b\u1ea3ng t\u1ed1n k\u00e9m.<\/p>\n

      \n
    • M\u1ee5c ti\u00eau:<\/strong>Gi\u1ea3m s\u1ed1 l\u01b0\u1ee3ng thao t\u00e1c n\u1ed1i c\u1ea7n thi\u1ebft cho c\u00e1c truy v\u1ea5n ph\u1ee9c t\u1ea1p.<\/li>\n
    • L\u1ee3i \u00edch:<\/strong>T\u1ed1c \u0111\u1ed9 thao t\u00e1c \u0111\u1ecdc nhanh h\u01a1n v\u00e0 logic truy v\u1ea5n \u0111\u01b0\u1ee3c \u0111\u01a1n gi\u1ea3n h\u00f3a.<\/li>\n
    • Chi ph\u00ed:<\/strong>T\u0103ng s\u1eed d\u1ee5ng dung l\u01b0\u1ee3ng l\u01b0u tr\u1eef v\u00e0 nguy c\u01a1 cao h\u01a1n v\u1ec1 s\u1ef1 b\u1ea5t nh\u1ea5t d\u1eef li\u1ec7u.<\/li>\n<\/ul>\n

      C\u00e2u h\u1ecfi & C\u00e2u tr\u1ea3 l\u1eddi: Kh\u00e1m ph\u00e1 s\u00e2u v\u1ec1 Chu\u1ea9n h\u00f3a v\u00e0 Thi\u1ebft k\u1ebf ERD \ud83d\udcdd<\/h2>\n

      Nh\u1eefng c\u00e2u h\u1ecfi n\u00e0y gi\u1ea3i quy\u1ebft c\u00e1c \u0111i\u1ec3m g\u00e2y kh\u00f3 kh\u0103n ph\u1ed5 bi\u1ebfn nh\u1ea5t khi thi\u1ebft k\u1ebf c\u00e1c l\u01b0\u1ee3c \u0111\u1ed3 quan h\u1ec7. Ch\u00fang bao qu\u00e1t qu\u00e1 tr\u00ecnh chuy\u1ec3n t\u1eeb l\u00fd thuy\u1ebft sang th\u1ef1c thi th\u1ef1c t\u1ebf.<\/p>\n

      C\u00e2u h\u1ecfi 1: T\u00f4i c\u00f3 c\u1ea7n chu\u1ea9n h\u00f3a m\u1ecdi th\u1ee9 \u0111\u1ebfn d\u1ea1ng chu\u1ea9n 3NF kh\u00f4ng? \ud83e\udd37\u200d\u2642\ufe0f<\/h3>\n

      C\u00e2u tr\u1ea3 l\u1eddi ng\u1eafn g\u1ecdn l\u00e0 kh\u00f4ng. M\u1eb7c d\u00f9 D\u1ea1ng chu\u1ea9n 3NF (3NF) l\u00e0 ti\u00eau chu\u1ea9n tham chi\u1ebfu cho nhi\u1ec1u \u1ee9ng d\u1ee5ng, nh\u01b0ng n\u00f3 kh\u00f4ng ph\u1ea3i l\u00e0 quy t\u1eafc c\u1ee9ng nh\u1eafc cho m\u1ecdi t\u00ecnh hu\u1ed1ng. Chu\u1ea9n h\u00f3a \u0111\u1ebfn 3NF lo\u1ea1i b\u1ecf c\u00e1c ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u, \u0111\u1ea3m b\u1ea3o r\u1eb1ng c\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng kh\u00f3a ch\u1ec9 ph\u1ee5 thu\u1ed9c v\u00e0o kh\u00f3a ch\u00ednh. Tuy nhi\u00ean, \u0111\u1ea1t \u0111\u01b0\u1ee3c c\u00e1c d\u1ea1ng cao h\u01a1n nh\u01b0 D\u1ea1ng chu\u1ea9n Boyce-Codd (BCNF) hay D\u1ea1ng chu\u1ea9n th\u1ee9 t\u01b0 (4NF) \u0111\u00f4i khi c\u00f3 th\u1ec3 l\u00e0m ph\u1ee9c t\u1ea1p l\u01b0\u1ee3c \u0111\u1ed3 m\u00e0 kh\u00f4ng mang l\u1ea1i l\u1ee3i \u00edch \u0111\u00e1ng k\u1ec3.<\/p>\n

      H\u00e3y c\u00e2n nh\u1eafc c\u00e1c \u0111i\u1ec3m trao \u0111\u1ed5i:<\/p>\n

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      • 3NF:<\/strong>Ph\u00f9 h\u1ee3p v\u1edbi c\u00e1c h\u1ec7 th\u1ed1ng giao d\u1ecbch \u0111a m\u1ee5c \u0111\u00edch n\u01a1i t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u l\u00e0 \u01b0u ti\u00ean h\u00e0ng \u0111\u1ea7u.<\/li>\n
      • 4NF\/5NF:<\/strong> Th\u01b0\u1eddng qu\u00e1 m\u1ee9c tr\u1eeb khi b\u1ea1n \u0111ang x\u1eed l\u00fd c\u00e1c ph\u1ee5 thu\u1ed9c \u0111a gi\u00e1 tr\u1ecb ph\u1ee9c t\u1ea1p ho\u1eb7c c\u00e1c ph\u1ee5 thu\u1ed9c k\u1ebft n\u1ed1i.<\/li>\n
      • C\u00e1ch ti\u1ebfp c\u1eadn th\u1ef1c t\u1ebf:<\/strong>Thi\u1ebft k\u1ebf theo 3NF tr\u01b0\u1edbc. \u0110\u00e1nh gi\u00e1 c\u00e1c \u0111i\u1ec3m ngh\u1ebdn hi\u1ec7u su\u1ea5t tr\u01b0\u1edbc khi c\u00e2n nh\u1eafc vi\u1ec7c lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a ho\u1eb7c chu\u1ea9n h\u00f3a th\u00eam.<\/li>\n<\/ul>\n

        C\u00e2u h\u1ecfi 2: Chu\u1ea9n h\u00f3a \u1ea3nh h\u01b0\u1edfng nh\u01b0 th\u1ebf n\u00e0o \u0111\u1ebfn hi\u1ec7u su\u1ea5t truy v\u1ea5n? \ud83d\udc22<\/h3>\n

        Chu\u1ea9n h\u00f3a \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn hi\u1ec7u su\u1ea5t ch\u1ee7 y\u1ebfu th\u00f4ng qua y\u00eau c\u1ea7u th\u1ef1c hi\u1ec7n c\u00e1c thao t\u00e1c k\u1ebft n\u1ed1i (join). Khi d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c ph\u00e2n b\u1ed1 tr\u00ean nhi\u1ec1u b\u1ea3ng, vi\u1ec7c truy xu\u1ea5t m\u1ed9t b\u1ea3n ghi \u0111\u1ea7y \u0111\u1ee7 \u0111\u00f2i h\u1ecfi b\u1ed9 \u0111\u1ed9ng c\u01a1 c\u01a1 s\u1edf d\u1eef li\u1ec7u ph\u1ea3i k\u1ebft n\u1ed1i c\u00e1c b\u1ea3ng n\u00e0y l\u1ea1i v\u1edbi nhau. Qu\u00e1 tr\u00ecnh n\u00e0y ti\u00eau t\u1ed1n t\u00e0i nguy\u00ean CPU v\u00e0 b\u1ed9 nh\u1edb.<\/p>\n

        C\u00e1c y\u1ebfu t\u1ed1 ch\u00ednh \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn hi\u1ec7u su\u1ea5t bao g\u1ed3m:<\/p>\n

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        • \u0110\u1ed9 ph\u1ee9c t\u1ea1p c\u1ee7a k\u1ebft n\u1ed1i (join):<\/strong>Nhi\u1ec1u b\u1ea3ng h\u01a1n ngh\u0129a l\u00e0 c\u00f3 nhi\u1ec1u \u0111i\u1ec1u ki\u1ec7n k\u1ebft n\u1ed1i c\u1ea7n \u0111\u00e1nh gi\u00e1 h\u01a1n.<\/li>\n
        • Ch\u1ec9 m\u1ee5c:<\/strong>C\u00e1c kh\u00f3a ngo\u1ea1i ph\u1ea3i \u0111\u01b0\u1ee3c l\u1eadp ch\u1ec9 m\u1ee5c \u0111\u1ec3 t\u0103ng t\u1ed1c c\u00e1c thao t\u00e1c k\u1ebft n\u1ed1i. Thi\u1ebfu ch\u1ec9 m\u1ee5c ph\u00f9 h\u1ee3p, chu\u1ea9n h\u00f3a c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn suy gi\u1ea3m hi\u1ec7u su\u1ea5t nghi\u00eam tr\u1ecdng.<\/li>\n
        • Dung l\u01b0\u1ee3ng d\u1eef li\u1ec7u:<\/strong>Khi t\u1eadp d\u1eef li\u1ec7u t\u0103ng l\u00ean, chi ph\u00ed qu\u00e9t v\u00e0 k\u1ebft n\u1ed1i s\u1ebd t\u0103ng \u0111\u00e1ng k\u1ec3.<\/li>\n<\/ul>\n

          Trong c\u00e1c \u1ee9ng d\u1ee5ng c\u00f3 nhi\u1ec1u thao t\u00e1c \u0111\u1ecdc, chi ph\u00ed n\u00e0y c\u00f3 th\u1ec3 tr\u1edf th\u00e0nh \u0111i\u1ec3m ngh\u1ebdn. Trong c\u00e1c \u1ee9ng d\u1ee5ng c\u00f3 nhi\u1ec1u thao t\u00e1c ghi, chi ph\u00ed n\u00e0y th\u01b0\u1eddng kh\u00f4ng \u0111\u00e1ng k\u1ec3 so v\u1edbi l\u1ee3i \u00edch t\u1eeb vi\u1ec7c gi\u1ea3m thi\u1ec3u c\u00e1c l\u1ed7i c\u1eadp nh\u1eadt.<\/p>\n

          C\u00e2u h\u1ecfi 3: Khi n\u00e0o th\u00ec ph\u00f9 h\u1ee3p \u0111\u1ec3 lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a? \u2699\ufe0f<\/h3>\n

          Lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a kh\u00f4ng n\u00ean l\u00e0 tr\u1ea1ng th\u00e1i m\u1eb7c \u0111\u1ecbnh. \u0110\u00e2y l\u00e0 bi\u1ec7n ph\u00e1p kh\u1eafc ph\u1ee5c \u0111\u01b0\u1ee3c \u00e1p d\u1ee5ng sau khi x\u00e1c \u0111\u1ecbnh \u0111\u01b0\u1ee3c c\u00e1c v\u1ea5n \u0111\u1ec1 hi\u1ec7u su\u1ea5t c\u1ee5 th\u1ec3. B\u1ea1n n\u00ean c\u00e2n nh\u1eafc lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a trong c\u00e1c t\u00ecnh hu\u1ed1ng sau:<\/p>\n

            \n
          • C\u00e1c t\u00e1c v\u1ee5 c\u00f3 nhi\u1ec1u thao t\u00e1c \u0111\u1ecdc:<\/strong>N\u1ebfu h\u1ec7 th\u1ed1ng x\u1eed l\u00fd h\u00e0ng ng\u00e0n thao t\u00e1c \u0111\u1ecdc cho m\u1ed7i thao t\u00e1c ghi, chi ph\u00ed c\u1ee7a c\u00e1c thao t\u00e1c k\u1ebft n\u1ed1i c\u00f3 th\u1ec3 v\u01b0\u1ee3t qu\u00e1 chi ph\u00ed l\u01b0u tr\u1eef.<\/li>\n
          • B\u1ea3ng \u0111i\u1ec1u khi\u1ec3n b\u00e1o c\u00e1o:<\/strong>C\u00e1c truy v\u1ea5n ph\u00e2n t\u00edch ph\u1ee9c t\u1ea1p th\u01b0\u1eddng \u0111\u01b0\u1ee3c l\u1ee3i t\u1eeb d\u1eef li\u1ec7u \u0111\u00e3 \u0111\u01b0\u1ee3c k\u1ebft n\u1ed1i tr\u01b0\u1edbc v\u00e0 l\u01b0u tr\u1eef trong c\u00e1c b\u1ea3ng r\u1ed9ng.<\/li>\n
          • C\u00e1c l\u1edbp b\u1ed9 nh\u1edb \u0111\u1ec7m:<\/strong>\u0110\u00f4i khi lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a \u0111\u01b0\u1ee3c tri\u1ec3n khai \u1edf l\u1edbp b\u1ed9 nh\u1edb \u0111\u1ec7m thay v\u00ec \u0111\u1ed9ng c\u01a1 l\u01b0u tr\u1eef ch\u00ednh.<\/li>\n
          • H\u1ea1n ch\u1ebf c\u1ee7a h\u1ec7 th\u1ed1ng c\u0169:<\/strong>C\u00e1c \u0111\u1ed9ng c\u01a1 c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u0169 ho\u1eb7c c\u00e1c gi\u1edbi h\u1ea1n ph\u1ea7n c\u1ee9ng c\u1ee5 th\u1ec3 c\u00f3 th\u1ec3 g\u1eb7p kh\u00f3 kh\u0103n v\u1edbi c\u00e1c thao t\u00e1c k\u1ebft n\u1ed1i ph\u1ee9c t\u1ea1p.<\/li>\n<\/ul>\n

            C\u00e2u h\u1ecfi 4: L\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 qu\u1ea3n l\u00fd t\u00ednh nh\u1ea5t qu\u00e1n d\u1eef li\u1ec7u trong qu\u00e1 tr\u00ecnh lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a? \ud83d\udee1\ufe0f<\/h3>\n

            Vi\u1ec7c th\u00eam t\u00ednh d\u01b0 th\u1eeba t\u1ea1o ra r\u1ee7i ro v\u1ec1 s\u1ef1 kh\u00f4ng nh\u1ea5t qu\u00e1n d\u1eef li\u1ec7u. N\u1ebfu b\u1ea1n l\u01b0u t\u00ean kh\u00e1ch h\u00e0ng trong c\u1ea3 b\u1ea3ng \u0110\u01a1n h\u00e0ng<\/em> v\u00e0 b\u1ea3ng Kh\u00e1ch h\u00e0ng<\/em> th\u00ec vi\u1ec7c c\u1eadp nh\u1eadt t\u00ean trong b\u1ea3ng Kh\u00e1ch h\u00e0ng<\/em> b\u1ea3ng y\u00eau c\u1ea7u c\u1eadp nh\u1eadt lan truy\u1ec1n \u0111\u1ebfn \u0110\u01a1n h\u00e0ng<\/em> b\u1ea3ng.<\/p>\n

            C\u00e1c chi\u1ebfn l\u01b0\u1ee3c \u0111\u1ec3 duy tr\u00ec t\u00ednh nh\u1ea5t qu\u00e1n bao g\u1ed3m:<\/p>\n

              \n
            • Logic \u1ee8ng d\u1ee5ng:<\/strong> \u0110\u1ea3m b\u1ea3o m\u00e3 \u1ee9ng d\u1ee5ng c\u1eadp nh\u1eadt t\u1ea5t c\u1ea3 c\u00e1c tr\u01b0\u1eddng d\u01b0 th\u1eeba trong m\u1ed9t giao d\u1ecbch duy nh\u1ea5t.<\/li>\n
            • B\u1ed9 k\u00edch ho\u1ea1t C\u01a1 s\u1edf d\u1eef li\u1ec7u:<\/strong> S\u1eed d\u1ee5ng b\u1ed9 k\u00edch ho\u1ea1t \u0111\u1ec3 \u0111\u1ed3ng b\u1ed9 t\u1ef1 \u0111\u1ed9ng c\u00e1c c\u1ed9t d\u01b0 th\u1eeba khi d\u1eef li\u1ec7u ngu\u1ed3n thay \u0111\u1ed5i.<\/li>\n
            • \u0110i\u1ec1u ch\u1ec9nh \u0111\u1ecbnh k\u1ef3:<\/strong> Ch\u1ea1y c\u00e1c c\u00f4ng vi\u1ec7c \u0111\u01b0\u1ee3c l\u00ean l\u1ecbch \u0111\u1ec3 ki\u1ec3m tra v\u00e0 kh\u1eafc ph\u1ee5c c\u00e1c b\u1ea5t nh\u1ea5t trong d\u1eef li\u1ec7u phi chu\u1ea9n h\u00f3a.<\/li>\n
            • Chuy\u00ean bi\u1ec7t h\u00f3a B\u1ea3n sao \u0111\u1ecdc:<\/strong> Gi\u1eef c\u01a1 s\u1edf d\u1eef li\u1ec7u ch\u00ednh ho\u00e0n to\u00e0n \u0111\u01b0\u1ee3c chu\u1ea9n h\u00f3a v\u00e0 s\u1eed d\u1ee5ng b\u1ea3n sao phi chu\u1ea9n h\u00f3a cho m\u1ee5c \u0111\u00edch b\u00e1o c\u00e1o.<\/li>\n<\/ul>\n

              C\u00e2u h\u1ecfi – Tr\u1ea3 l\u1eddi: C\u00e1c t\u00ecnh hu\u1ed1ng n\u00e2ng cao v\u00e0 s\u1ef1 \u0111\u00e1nh \u0111\u1ed5i \u2696\ufe0f<\/h2>\n

              V\u01b0\u1ee3t ra ngo\u00e0i nh\u1eefng ki\u1ebfn th\u1ee9c c\u01a1 b\u1ea3n, nh\u1eefng th\u00e1ch th\u1ee9c ki\u1ebfn tr\u00fac c\u1ee5 th\u1ec3 n\u1ea3y sinh khi m\u1edf r\u1ed9ng h\u1ec7 th\u1ed1ng. Nh\u1eefng c\u00e2u h\u1ecfi n\u00e0y \u0111\u1ec1 c\u1eadp \u0111\u1ebfn nh\u1eefng chi ti\u1ebft tinh t\u1ebf \u0111\u00f3.<\/p>\n

              C\u00e2u h\u1ecfi 5: T\u00f4i c\u00f3 th\u1ec3 k\u1ebft h\u1ee3p c\u00e1c b\u1ea3ng chu\u1ea9n h\u00f3a v\u00e0 phi chu\u1ea9n h\u00f3a trong c\u00f9ng m\u1ed9t s\u01a1 \u0111\u1ed3 ERD kh\u00f4ng? \ud83e\udde9<\/h3>\n

              C\u00f3, c\u00e1c m\u00f4 h\u00ecnh lai th\u01b0\u1eddng g\u1eb7p trong m\u00f4i tr\u01b0\u1eddng s\u1ea3n xu\u1ea5t. Vi\u1ec7c duy tr\u00ec m\u1ed9t l\u01b0\u1ee3c \u0111\u1ed3 chu\u1ea9n h\u00f3a c\u1ed1t l\u00f5i \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o t\u00ednh to\u00e0n v\u1eb9n giao d\u1ecbch l\u00e0 c\u00e1ch l\u00e0m chu\u1ea9n, \u0111\u1ed3ng th\u1eddi t\u1ea1o ra c\u00e1c view phi chu\u1ea9n h\u00f3a ho\u1eb7c b\u1ea3ng t\u1ed5ng h\u1ee3p cho c\u00e1c tr\u01b0\u1eddng h\u1ee3p s\u1eed d\u1ee5ng c\u1ee5 th\u1ec3.<\/p>\n

              V\u00ed d\u1ee5:<\/p>\n

                \n
              • B\u1ea3ng c\u1ed1t l\u00f5i:<\/strong> Gi\u1eef b\u1ea3ng ng\u01b0\u1eddi d\u00f9ng, s\u1ea3n ph\u1ea9m v\u00e0 \u0111\u01a1n h\u00e0ng \u1edf d\u1ea1ng chu\u1ea9n h\u00f3a c\u1ea5p 3 (3NF) \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o c\u00e1c ghi ch\u00e9p t\u00e0i ch\u00ednh ch\u00ednh x\u00e1c.<\/li>\n
              • B\u1ea3ng b\u00e1o c\u00e1o:<\/strong> T\u1ea1o m\u1ed9t b\u1ea3ng phi chu\u1ea9n h\u00f3a t\u1ed5ng h\u1ee3p t\u1ed5ng \u0111\u01a1n h\u00e0ng v\u00e0 th\u00f4ng tin kh\u00e1ch h\u00e0ng \u0111\u1ec3 hi\u1ec3n th\u1ecb b\u1ea3ng \u0111i\u1ec1u khi\u1ec3n nhanh ch\u00f3ng.<\/li>\n
              • Views:<\/strong> S\u1eed d\u1ee5ng c\u00e1c view SQL \u0111\u1ec3 tr\u00ecnh b\u00e0y c\u1ea5u tr\u00fac phi chu\u1ea9n h\u00f3a cho \u1ee9ng d\u1ee5ng m\u00e0 kh\u00f4ng c\u1ea7n sao ch\u00e9p d\u1eef li\u1ec7u v\u1eadt l\u00fd.<\/li>\n<\/ul>\n

                C\u00e2u h\u1ecfi 6: Vi\u1ec7c phi chu\u1ea9n h\u00f3a c\u00f3 vi ph\u1ea1m l\u00fd thuy\u1ebft c\u01a1 s\u1edf d\u1eef li\u1ec7u kh\u00f4ng? \ud83d\udcda<\/h3>\n

                V\u1ec1 m\u1eb7t l\u00fd thuy\u1ebft, c\u00f3. L\u00fd thuy\u1ebft quan h\u1ec7 \u1ee7ng h\u1ed9 chu\u1ea9n h\u00f3a \u0111\u1ec3 gi\u1ea3m thi\u1ec3u c\u00e1c b\u1ea5t th\u01b0\u1eddng. Tuy nhi\u00ean, k\u1ef9 thu\u1eadt th\u1ef1c t\u1ebf th\u01b0\u1eddng \u0111\u00f2i h\u1ecfi ph\u1ea3i l\u00e0m m\u1ec1m c\u00e1c quy t\u1eafc n\u00e0y \u0111\u1ec3 \u0111\u00e1p \u1ee9ng c\u00e1c SLA v\u1ec1 hi\u1ec7u su\u1ea5t. Vi\u1ec7c vi ph\u1ea1m n\u00e0y l\u00e0 c\u00f3 ch\u1ee7 \u00fd v\u00e0 \u0111\u01b0\u1ee3c t\u00ednh to\u00e1n k\u1ef9 l\u01b0\u1ee1ng. Mi\u1ec5n l\u00e0 s\u1ef1 d\u01b0 th\u1eeba \u0111\u01b0\u1ee3c qu\u1ea3n l\u00fd v\u00e0 ghi ch\u00e9p r\u00f5 r\u00e0ng, thi\u1ebft k\u1ebf v\u1eabn h\u1ee3p l\u1ec7 cho m\u1ee5c \u0111\u00edch s\u1eed d\u1ee5ng c\u1ee7a n\u00f3.<\/p>\n

                C\u00e2u h\u1ecfi 7: Ch\u1ec9 m\u1ee5c t\u01b0\u01a1ng t\u00e1c nh\u01b0 th\u1ebf n\u00e0o v\u1edbi chu\u1ea9n h\u00f3a? \ud83d\udd16<\/h3>\n

                Ch\u1ec9 m\u1ee5c l\u00e0 c\u00f4ng c\u1ee5 ch\u00ednh \u0111\u1ec3 gi\u1ea3m thi\u1ec3u chi ph\u00ed hi\u1ec7u su\u1ea5t do chu\u1ea9n h\u00f3a g\u00e2y ra. Khi b\u1ea1n chu\u1ea9n h\u00f3a, b\u1ea1n t\u1ea1o ra c\u00e1c kh\u00f3a ngo\u1ea1i. Nh\u1eefng kh\u00f3a ngo\u1ea1i n\u00e0y ph\u1ea3i \u0111\u01b0\u1ee3c ch\u1ec9 m\u1ee5c \u0111\u1ec3 cho ph\u00e9p vi\u1ec7c n\u1ed1i (join) hi\u1ec7u qu\u1ea3.<\/p>\n

                Xem x\u00e9t c\u00e1c \u0111i\u1ec3m sau:<\/p>\n

                  \n
                • Ch\u1ec9 m\u1ee5c Kh\u00f3a ngo\u1ea1i:<\/strong> M\u1ed7i kh\u00f3a ngo\u1ea1i \u0111\u1ec1u n\u00ean c\u00f3 ch\u1ec9 m\u1ee5c \u0111\u1ec3 t\u0103ng t\u1ed1c \u0111\u1ed9 n\u1ed1i.<\/li>\n
                • Ch\u1ec9 m\u1ee5c k\u1ebft h\u1ee3p:<\/strong> N\u1ebfu m\u1ed9t truy v\u1ea5n k\u1ebft h\u1ee3p tr\u00ean nhi\u1ec1u c\u1ed9t, ch\u1ec9 m\u1ee5c k\u1ebft h\u1ee3p c\u00f3 th\u1ec3 bao ph\u1ee7 t\u1ea5t c\u1ea3 c\u00e1c \u0111i\u1ec1u ki\u1ec7n k\u1ebft h\u1ee3p.<\/li>\n
                • T\u00e1c \u0111\u1ed9ng c\u1ee7a vi\u1ec7c lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a:<\/strong> Vi\u1ec7c lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a th\u01b0\u1eddng gi\u1ea3m nhu c\u1ea7u v\u1ec1 ch\u1ec9 m\u1ee5c kh\u00f3a ngo\u1ea1i, c\u00f3 th\u1ec3 l\u00e0m gi\u1ea3m chi ph\u00ed ghi tr\u00ean ch\u1ec9 m\u1ee5c.<\/li>\n<\/ul>\n

                  So s\u00e1nh: Chu\u1ea9n h\u00f3a so v\u1edbi lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a \ud83d\udccb<\/h2>\n

                  \u0110\u1ec3 tr\u1ef1c quan h\u00f3a r\u00f5 r\u00e0ng c\u00e1c \u0111i\u1ec3m \u0111\u00e1nh \u0111\u1ed5i, h\u00e3y tham kh\u1ea3o b\u1ea3ng d\u01b0\u1edbi \u0111\u00e2y. C\u1ea5u tr\u00fac n\u00e0y gi\u00fap h\u1ed7 tr\u1ee3 ra quy\u1ebft \u0111\u1ecbnh trong giai \u0111o\u1ea1n thi\u1ebft k\u1ebf.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n
                  T\u00ednh n\u0103ng<\/th>\nChu\u1ea9n h\u00f3a<\/th>\nLo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a<\/th>\n<\/tr>\n<\/thead>\n
                  S\u1ef1 tr\u00f9ng l\u1eb7p d\u1eef li\u1ec7u<\/strong><\/td>\nT\u1ed1i thi\u1ec3u h\u00f3a<\/td>\nT\u0103ng l\u00ean<\/td>\n<\/tr>\n
                  \u0110\u1ed9 to\u00e0n v\u1eb9n d\u1eef li\u1ec7u<\/strong><\/td>\nCao<\/td>\nY\u00eau c\u1ea7u qu\u1ea3n l\u00fd<\/td>\n<\/tr>\n
                  Kh\u00f4ng gian l\u01b0u tr\u1eef<\/strong><\/td>\nHi\u1ec7u qu\u1ea3<\/td>\nKh\u00f4ng hi\u1ec7u qu\u1ea3 h\u01a1n<\/td>\n<\/tr>\n
                  Hi\u1ec7u su\u1ea5t \u0111\u1ecdc<\/strong><\/td>\nCh\u1eadm h\u01a1n (nhi\u1ec1u ph\u00e9p n\u1ed1i h\u01a1n)<\/td>\nNhanh h\u01a1n (\u00edt ph\u00e9p n\u1ed1i h\u01a1n)<\/td>\n<\/tr>\n
                  Hi\u1ec7u su\u1ea5t ghi<\/strong><\/td>\nNhanh h\u01a1n (\u00edt d\u1eef li\u1ec7u c\u1ea7n c\u1eadp nh\u1eadt)<\/td>\nCh\u1eadm h\u01a1n (c\u1eadp nh\u1eadt t\u1ea5t c\u1ea3 b\u1ea3n sao)<\/td>\n<\/tr>\n
                  \u0110\u1ed9 ph\u1ee9c t\u1ea1p<\/strong><\/td>\nCao (nhi\u1ec1u b\u1ea3ng)<\/td>\nCao (logic \u0111\u1ec3 \u0111\u1ed3ng b\u1ed9 d\u1eef li\u1ec7u)<\/td>\n<\/tr>\n
                  Tr\u01b0\u1eddng h\u1ee3p s\u1eed d\u1ee5ng t\u1ed1t nh\u1ea5t<\/strong><\/td>\nOLTP, H\u1ec7 th\u1ed1ng giao d\u1ecbch<\/td>\nOLAP, B\u00e1o c\u00e1o, Tr\u1ecdng t\u1ea3i \u0111\u1ecdc cao<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

                  Chi\u1ebfn l\u01b0\u1ee3c tri\u1ec3n khai: C\u00e1ch ti\u1ebfp c\u1eadn t\u1eebng b\u01b0\u1edbc \ud83d\ude80<\/h2>\n

                  Thi\u1ebft k\u1ebf m\u1ed9t l\u01b0\u1ee3c \u0111\u1ed3 y\u00eau c\u1ea7u m\u1ed9t quy tr\u00ecnh c\u00f3 h\u1ec7 th\u1ed1ng. \u0110\u1eebng v\u1ed9i v\u00e0ng \u0111\u1ec3 lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a. Tu\u00e2n theo c\u00e1ch ti\u1ebfp c\u1eadn c\u00f3 c\u1ea5u tr\u00fac n\u00e0y \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o n\u1ec1n t\u1ea3ng \u1ed5n \u0111\u1ecbnh.<\/p>\n

                  B\u01b0\u1edbc 1: M\u00f4 h\u00ecnh h\u00f3a v\u00ec t\u00ednh to\u00e0n v\u1eb9n tr\u01b0\u1edbc ti\u00ean \ud83c\udfd7\ufe0f<\/h3>\n

                  B\u1eaft \u0111\u1ea7u b\u1eb1ng c\u00e1ch t\u1ea1o m\u1ed9t l\u01b0\u1ee3c \u0111\u1ed3 \u0111\u01b0\u1ee3c chu\u1ea9n h\u00f3a ho\u00e0n to\u00e0n. Nh\u1eafm \u0111\u1ebfn \u00edt nh\u1ea5t d\u1ea1ng chu\u1ea9n h\u00f3a th\u1ee9 ba (3NF). X\u00e1c \u0111\u1ecbnh t\u1ea5t c\u1ea3 c\u00e1c th\u1ef1c th\u1ec3, thu\u1ed9c t\u00ednh v\u00e0 m\u1ed1i quan h\u1ec7. \u0110\u1ea3m b\u1ea3o m\u1ecdi b\u1ea3ng \u0111\u1ec1u c\u00f3 kh\u00f3a ch\u00ednh v\u00e0 c\u00e1c kh\u00f3a ngo\u1ea1i \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh ch\u00ednh x\u00e1c. Giai \u0111o\u1ea1n n\u00e0y \u0111\u1ea3m b\u1ea3o d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n ch\u00ednh x\u00e1c v\u00e0 nh\u1ea5t qu\u00e1n.<\/p>\n

                  B\u01b0\u1edbc 2: Ph\u00e2n t\u00edch c\u00e1c m\u1eabu truy v\u1ea5n \ud83d\udd0e<\/h3>\n

                  Tr\u01b0\u1edbc khi thay \u0111\u1ed5i l\u01b0\u1ee3c \u0111\u1ed3, h\u00e3y hi\u1ec3u c\u00e1ch d\u1eef li\u1ec7u s\u1ebd \u0111\u01b0\u1ee3c truy c\u1eadp. Xem l\u1ea1i y\u00eau c\u1ea7u \u1ee9ng d\u1ee5ng v\u00e0 nh\u1eadt k\u00fd truy v\u1ea5n. X\u00e1c \u0111\u1ecbnh c\u00e1c truy v\u1ea5n n\u00e0o ch\u1eadm ho\u1eb7c ph\u1ee9c t\u1ea1p. T\u00ecm ki\u1ebfm c\u00e1c m\u1eabu m\u00e0 nhi\u1ec1u ph\u00e9p n\u1ed1i (join) th\u01b0\u1eddng xuy\u00ean \u0111\u01b0\u1ee3c y\u00eau c\u1ea7u.<\/p>\n

                  B\u01b0\u1edbc 3: T\u1ed1i \u01b0u h\u00f3a ch\u1ec9 m\u1ee5c \u26a1<\/h3>\n

                  Tr\u01b0\u1edbc khi lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a, h\u00e3y \u0111\u1ea3m b\u1ea3o l\u01b0\u1ee3c \u0111\u1ed3 \u0111\u00e3 chu\u1ea9n h\u00f3a c\u1ee7a b\u1ea1n \u0111\u01b0\u1ee3c ch\u1ec9 m\u1ee5c \u0111\u00fang c\u00e1ch. Th\u01b0\u1eddng xuy\u00ean, vi\u1ec7c th\u00eam c\u00e1c ch\u1ec9 m\u1ee5c h\u1ee3p l\u00fd (composite indexes) s\u1ebd gi\u1ea3i quy\u1ebft c\u00e1c v\u1ea5n \u0111\u1ec1 hi\u1ec7u su\u1ea5t m\u00e0 kh\u00f4ng c\u1ea7n thay \u0111\u1ed5i c\u1ea5u tr\u00fac b\u1ea3ng. Ki\u1ec3m th\u1eed c\u00e1c truy v\u1ea5n v\u1edbi l\u01b0\u1ee3c \u0111\u1ed3 v\u00e0 ch\u1ec9 m\u1ee5c hi\u1ec7n t\u1ea1i \u0111\u1ec3 thi\u1ebft l\u1eadp n\u1ec1n t\u1ea3ng tham chi\u1ebfu.<\/p>\n

                  B\u01b0\u1edbc 4: Lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a c\u00f3 m\u1ee5c ti\u00eau \ud83c\udfaf<\/h3>\n

                  N\u1ebfu hi\u1ec7u su\u1ea5t v\u1eabn ch\u01b0a \u0111\u1ee7, h\u00e3y \u00e1p d\u1ee5ng lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a m\u1ed9t c\u00e1ch c\u00f3 ch\u1ecdn l\u1ecdc. \u0110\u1eebng lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a to\u00e0n b\u1ed9 c\u01a1 s\u1edf d\u1eef li\u1ec7u. Ch\u1ec9 t\u1eadp trung v\u00e0o c\u00e1c b\u1ea3ng ho\u1eb7c c\u1ed9t c\u1ee5 th\u1ec3 g\u00e2y ra \u0111i\u1ec3m ngh\u1ebdn. Ghi ch\u00e9p l\u1ea1i m\u1ecdi thay \u0111\u1ed5i \u0111\u1ec3 ph\u1ee5c v\u1ee5 b\u1ea3o tr\u00ec trong t\u01b0\u01a1ng lai.<\/p>\n

                  B\u01b0\u1edbc 5: Gi\u00e1m s\u00e1t v\u00e0 l\u1eb7p l\u1ea1i \ud83d\udcc8<\/h3>\n

                  Thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u kh\u00f4ng ph\u1ea3i l\u00e0 t\u0129nh. Gi\u00e1m s\u00e1t h\u1ec7 th\u1ed1ng theo th\u1eddi gian. Khi kh\u1ed1i l\u01b0\u1ee3ng d\u1eef li\u1ec7u t\u0103ng ho\u1eb7c m\u1eabu s\u1eed d\u1ee5ng thay \u0111\u1ed5i, s\u1ef1 c\u00e2n b\u1eb1ng c\u00f3 th\u1ec3 c\u1ea7n \u0111i\u1ec1u ch\u1ec9nh. Th\u01b0\u1eddng xuy\u00ean xem x\u00e9t l\u1ea1i l\u01b0\u1ee3c \u0111\u1ed3 \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o n\u00f3 v\u1eabn \u0111\u00e1p \u1ee9ng c\u00e1c y\u00eau c\u1ea7u v\u1ec1 hi\u1ec7u su\u1ea5t v\u00e0 t\u00ednh to\u00e0n v\u1eb9n.<\/p>\n

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

                  Ngay c\u1ea3 nh\u1eefng nh\u00e0 thi\u1ebft k\u1ebf c\u00f3 kinh nghi\u1ec7m c\u0169ng c\u00f3 th\u1ec3 v\u1ea5p ng\u00e3 khi x\u1eed l\u00fd t\u1ed1i \u01b0u h\u00f3a s\u01a1 \u0111\u1ed3 ERD. H\u00e3y c\u1ea3nh gi\u00e1c v\u1edbi nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn n\u00e0y.<\/p>\n

                    \n
                  • Chu\u1ea9n h\u00f3a qu\u00e1 m\u1ee9c:<\/strong>T\u1ea1o qu\u00e1 nhi\u1ec1u b\u1ea3ng khi\u1ebfn l\u01b0\u1ee3c \u0111\u1ed3 tr\u1edf n\u00ean kh\u00f3 hi\u1ec3u v\u00e0 truy v\u1ea5n. Gi\u1eef c\u1ea5u tr\u00fac cho h\u1ee3p l\u00fd v\u00e0 tr\u1ef1c quan.<\/li>\n
                  • Chu\u1ea9n h\u00f3a thi\u1ebfu m\u1ee9c:<\/strong>L\u01b0u tr\u1eef qu\u00e1 nhi\u1ec1u d\u1eef li\u1ec7u trong m\u1ed9t b\u1ea3ng duy nh\u1ea5t d\u1eabn \u0111\u1ebfn hi\u1ec7n t\u01b0\u1ee3ng b\u1ea5t th\u01b0\u1eddng khi c\u1eadp nh\u1eadt v\u00e0 l\u00e3ng ph\u00ed kh\u00f4ng gian.<\/li>\n
                  • B\u1ecf qua s\u1ef1 t\u0103ng tr\u01b0\u1edfng d\u1eef li\u1ec7u:<\/strong>M\u1ed9t thi\u1ebft k\u1ebf ho\u1ea1t \u0111\u1ed9ng t\u1ed1t v\u1edbi 1.000 b\u1ea3n ghi c\u00f3 th\u1ec3 th\u1ea5t b\u1ea1i v\u1edbi 1.000.000. H\u00e3y l\u00ean k\u1ebf ho\u1ea1ch cho kh\u1ea3 n\u0103ng m\u1edf r\u1ed9ng.<\/li>\n
                  • Lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a \u1ea9n:<\/strong>Lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a m\u00e0 kh\u00f4ng c\u00f3 t\u00e0i li\u1ec7u d\u1eabn \u0111\u1ebfn s\u1ef1 nh\u1ea7m l\u1eabn. Nh\u1eefng ng\u01b0\u1eddi b\u1ea3o tr\u00ec trong t\u01b0\u01a1ng lai c\u00f3 th\u1ec3 kh\u00f4ng hi\u1ec3u t\u1ea1i sao d\u1eef li\u1ec7u b\u1ecb tr\u00f9ng l\u1eb7p.<\/li>\n
                  • Gi\u1ea3 \u0111\u1ecbnh m\u1ecdi truy v\u1ea5n \u0111\u1ec1u nh\u01b0 nhau:<\/strong>Kh\u00f4ng ph\u1ea3i m\u1ecdi truy v\u1ea5n n\u00e0o c\u0169ng c\u00f3 c\u00f9ng y\u00eau c\u1ea7u hi\u1ec7u su\u1ea5t. \u01afu ti\u00ean c\u00e1c truy v\u1ea5n th\u01b0\u1eddng xuy\u00ean v\u00e0 quan tr\u1ecdng nh\u1ea5t.<\/li>\n<\/ul>\n

                    Suy ngh\u0129 cu\u1ed1i c\u00f9ng v\u1ec1 ki\u1ebfn tr\u00fac l\u01b0\u1ee3c \u0111\u1ed3 \ud83e\udde0<\/h2>\n

                    Quy\u1ebft \u0111\u1ecbnh gi\u1eefa chu\u1ea9n h\u00f3a v\u00e0 lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a kh\u00f4ng ph\u1ea3i l\u00e0 nh\u1ecb ph\u00e2n. \u0110\u00f3 l\u00e0 m\u1ed9t ph\u1ed5 c\u00e1c th\u1ecfa hi\u1ec7p ph\u1ee5 thu\u1ed9c v\u00e0o nhu c\u1ea7u c\u1ee5 th\u1ec3 c\u1ee7a \u1ee9ng d\u1ee5ng c\u1ee7a b\u1ea1n. M\u1ed9t s\u01a1 \u0111\u1ed3 ERD \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf t\u1ed1t c\u00e2n b\u1eb1ng gi\u1eefa t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u v\u00e0 hi\u1ec7u qu\u1ea3 truy v\u1ea5n. B\u1eb1ng c\u00e1ch hi\u1ec3u r\u00f5 c\u00e1c nguy\u00ean t\u1eafc n\u1ec1n t\u1ea3ng v\u00e0 tu\u00e2n theo c\u00e1ch ti\u1ebfp c\u1eadn c\u00f3 c\u1ea5u tr\u00fac, b\u1ea1n c\u00f3 th\u1ec3 x\u00e2y d\u1ef1ng c\u00e1c h\u1ec7 th\u1ed1ng v\u1eeba v\u1eefng ch\u1eafc v\u1eeba hi\u1ec7u su\u1ea5t cao.<\/p>\n

                    H\u00e3y nh\u1edb r\u1eb1ng c\u00f4ng c\u1ee5 v\u00e0 c\u00f4ng ngh\u1ec7 lu\u00f4n thay \u0111\u1ed5i. Tuy nhi\u00ean, c\u00e1c nguy\u00ean t\u1eafc thi\u1ebft k\u1ebf quan h\u1ec7 v\u1eabn lu\u00f4n \u1ed5n \u0111\u1ecbnh. H\u00e3y t\u1eadp trung v\u00e0o m\u00f4 h\u00ecnh d\u1eef li\u1ec7u ch\u1ee9 kh\u00f4ng ph\u1ea3i v\u00e0o kh\u1ea3 n\u0103ng c\u1ee7a b\u1ed9 \u0111\u1ed9ng c\u01a1 c\u01a1 s\u1edf d\u1eef li\u1ec7u. M\u1ed9t n\u1ec1n t\u1ea3ng v\u1eefng ch\u1eafc s\u1ebd h\u1ed7 tr\u1ee3 \u1ee9ng d\u1ee5ng c\u1ee7a b\u1ea1n b\u1ea5t k\u1ec3 nh\u1eefng thay \u0111\u1ed5i h\u1ea1 t\u1ea7ng n\u00e0o x\u1ea3y ra trong t\u01b0\u01a1ng lai. Gi\u1eef l\u01b0\u1ee3c \u0111\u1ed3 s\u1ea1ch s\u1ebd, t\u00e0i li\u1ec7u r\u00f5 r\u00e0ng v\u00e0 lu\u00f4n ghi nh\u1edb c\u00e1c ch\u1ec9 s\u1ed1 hi\u1ec7u su\u1ea5t \u1edf m\u1ed7i b\u01b0\u1edbc. \ud83c\udf1f<\/p>\n","protected":false},"excerpt":{"rendered":"

                    Thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u l\u00e0 n\u1ec1n t\u1ea3ng c\u1ee7a b\u1ea5t k\u1ef3 \u1ee9ng d\u1ee5ng m\u1ea1nh m\u1ebd n\u00e0o. Khi x\u00e2y d\u1ef1ng S\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 (ERD), hai l\u1ef1c l\u01b0\u1ee3ng…<\/p>\n","protected":false},"author":1,"featured_media":86,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_yoast_wpseo_title":"Chu\u1ea9n h\u00f3a so v\u1edbi lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a trong s\u01a1 \u0111\u1ed3 ER \ud83d\udcca","_yoast_wpseo_metadesc":"B\u1ed1i r\u1ed1i v\u1ec1 thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u? H\u1ecdc khi n\u00e0o n\u00ean chu\u1ea9n h\u00f3a hay lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a trong s\u01a1 \u0111\u1ed3 ER. H\u01b0\u1edbng d\u1eabn chuy\u00ean gia v\u1ec1 t\u1ed1i \u01b0u h\u00f3a l\u01b0\u1ee3c \u0111\u1ed3, hi\u1ec7u su\u1ea5t v\u00e0 t\u00ednh to\u00e0n v\u1eb9n.","inline_featured_image":false,"fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[6],"tags":[10,11],"class_list":["post-85","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-erd","tag-academic","tag-erd"],"yoast_head":"\nChu\u1ea9n h\u00f3a so v\u1edbi lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a trong s\u01a1 \u0111\u1ed3 ER \ud83d\udcca<\/title>\n<meta name=\"description\" content=\"B\u1ed1i r\u1ed1i v\u1ec1 thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u? H\u1ecdc khi n\u00e0o n\u00ean chu\u1ea9n h\u00f3a hay lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a trong s\u01a1 \u0111\u1ed3 ER. H\u01b0\u1edbng d\u1eabn chuy\u00ean gia v\u1ec1 t\u1ed1i \u01b0u h\u00f3a l\u01b0\u1ee3c \u0111\u1ed3, hi\u1ec7u su\u1ea5t v\u00e0 t\u00ednh to\u00e0n v\u1eb9n.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.we-notes.com\/vn\/normalization-denormalization-erd-guide\/\" \/>\n<meta property=\"og:locale\" content=\"vi_VN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Chu\u1ea9n h\u00f3a so v\u1edbi lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a trong s\u01a1 \u0111\u1ed3 ER \ud83d\udcca\" \/>\n<meta property=\"og:description\" content=\"B\u1ed1i r\u1ed1i v\u1ec1 thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u? H\u1ecdc khi n\u00e0o n\u00ean chu\u1ea9n h\u00f3a hay lo\u1ea1i b\u1ecf chu\u1ea9n h\u00f3a trong s\u01a1 \u0111\u1ed3 ER. 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