{"id":1575,"date":"2026-03-25T23:10:52","date_gmt":"2026-03-25T23:10:52","guid":{"rendered":"https:\/\/www.viz-read.com\/vi\/erd-performance-query-speed\/"},"modified":"2026-03-25T23:10:52","modified_gmt":"2026-03-25T23:10:52","slug":"erd-performance-query-speed","status":"publish","type":"post","link":"https:\/\/www.viz-read.com\/vi\/erd-performance-query-speed\/","title":{"rendered":"ERD v\u00e0 Hi\u1ec7u su\u1ea5t: C\u00e1ch C\u00e1c L\u1ef1a ch\u1ecdn Thi\u1ebft k\u1ebf \u1ea2nh h\u01b0\u1edfng \u0111\u1ebfn T\u1ed1c \u0111\u1ed9 Truy v\u1ea5n"},"content":{"rendered":"

M\u00f4 h\u00ecnh h\u00f3a d\u1eef li\u1ec7u th\u01b0\u1eddng \u0111\u01b0\u1ee3c xem nh\u01b0 m\u1ed9t b\u00e0i t\u1eadp t\u0129nh nh\u1eb1m x\u00e1c \u0111\u1ecbnh c\u00e1c m\u1ed1i quan h\u1ec7 v\u00e0 th\u1ef1c th\u1ec3. Tuy nhi\u00ean, s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 (ERD) kh\u00f4ng ch\u1ec9 \u0111\u01a1n thu\u1ea7n l\u00e0 b\u1ea3n v\u1ebd thi\u1ebft k\u1ebf l\u01b0u tr\u1eef; n\u00f3 l\u00e0 y\u1ebfu t\u1ed1 quy\u1ebft \u0111\u1ecbnh tr\u1ef1c ti\u1ebfp \u0111\u1ebfn hi\u1ec7u qu\u1ea3 m\u00e0 m\u1ed9t b\u1ed9 \u0111\u1ed9ng c\u01a1 c\u01a1 s\u1edf d\u1eef li\u1ec7u truy xu\u1ea5t v\u00e0 thao t\u00e1c th\u00f4ng tin. M\u1ed7i \u0111\u01b0\u1eddng k\u1ebb, m\u1ed1i quan h\u1ec7 \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh v\u00e0 ki\u1ec3u d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c ch\u1ecdn \u0111\u1ec1u \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn k\u1ebf ho\u1ea1ch th\u1ef1c thi truy v\u1ea5n c\u1ee7a b\u1ea1n. Hi\u1ec3u r\u00f5 c\u01a1 ch\u1ebf \u0111\u1eb1ng sau thi\u1ebft k\u1ebf l\u01b0\u1ee3c \u0111\u1ed3 cho ph\u00e9p x\u00e2y d\u1ef1ng c\u00e1c h\u1ec7 th\u1ed1ng c\u00f3 kh\u1ea3 n\u0103ng m\u1edf r\u1ed9ng tr\u01a1n tru d\u01b0\u1edbi t\u1ea3i.<\/p>\n

H\u01b0\u1edbng d\u1eabn n\u00e0y kh\u00e1m ph\u00e1 m\u1ed1i quan h\u1ec7 k\u1ef9 thu\u1eadt gi\u1eefa c\u1ea5u tr\u00fac ERD v\u00e0 hi\u1ec7u su\u1ea5t truy v\u1ea5n. Ch\u00fang ta s\u1ebd \u0111i xa h\u01a1n c\u00e1c \u0111\u1ecbnh ngh\u0129a c\u01a1 b\u1ea3n \u0111\u1ec3 ph\u00e2n t\u00edch c\u00e1ch c\u00e1c quy\u1ebft \u0111\u1ecbnh m\u00f4 h\u00ecnh h\u00f3a c\u1ee5 th\u1ec3 \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn c\u00e1c thao t\u00e1c I\/O, s\u1eed d\u1ee5ng CPU v\u00e0 c\u01a1 ch\u1ebf kh\u00f3a trong m\u00f4i tr\u01b0\u1eddng quan h\u1ec7.<\/p>\n

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

1. N\u1ec1n t\u1ea3ng: C\u1ea5u tr\u00fac L\u01b0\u1ee3c \u0111\u1ed3 v\u00e0 L\u01b0u tr\u1eef V\u1eadt l\u00fd \ud83c\udfd7\ufe0f<\/h2>\n

Thi\u1ebft k\u1ebf logic b\u1ea1n t\u1ea1o trong ERD c\u1ee7a m\u00ecnh cu\u1ed1i c\u00f9ng s\u1ebd \u0111\u01b0\u1ee3c chuy\u1ec3n \u0111\u1ed5i th\u00e0nh c\u00e1c t\u1ec7p v\u1eadt l\u00fd tr\u00ean \u0111\u0129a. B\u1ed9 \u0111\u1ed9ng c\u01a1 c\u01a1 s\u1edf d\u1eef li\u1ec7u ph\u1ea3i \u00e1nh x\u1ea1 c\u00e1c th\u1ef1c th\u1ec3 logic n\u00e0y th\u00e0nh c\u00e1c trang, kh\u1ed1i v\u00e0 h\u00e0ng. Khi l\u01b0\u1ee3c \u0111\u1ed3 \u0111\u01b0\u1ee3c t\u1ed1i \u01b0u h\u00f3a, b\u1ed9 \u0111\u1ed9ng c\u01a1 s\u1ebd gi\u1ea3m thi\u1ec3u s\u1ed1 l\u1ea7n \u0111\u1ecdc \u0111\u0129a c\u1ea7n thi\u1ebft \u0111\u1ec3 \u0111\u00e1p \u1ee9ng m\u1ed9t y\u00eau c\u1ea7u. Ng\u01b0\u1ee3c l\u1ea1i, n\u1ebfu kh\u00f4ng \u0111\u01b0\u1ee3c t\u1ed1i \u01b0u h\u00f3a, b\u1ed9 \u0111\u1ed9ng c\u01a1 c\u00f3 th\u1ec3 b\u1ecb bu\u1ed9c ph\u1ea3i th\u1ef1c hi\u1ec7n qu\u00e9t to\u00e0n b\u1ed9 b\u1ea3ng, m\u1ed9t thao t\u00e1c t\u1ed1n k\u00e9m.<\/p>\n

H\u00e3y xem x\u00e9t kh\u00f3a ch\u00ednh. N\u00f3 \u0111\u00f3ng vai tr\u00f2 l\u00e0 \u0111\u1ecbnh danh duy nh\u1ea5t cho m\u1ed9t h\u00e0ng. Trong nhi\u1ec1u b\u1ed9 \u0111\u1ed9ng c\u01a1 l\u01b0u tr\u1eef, kh\u00f3a ch\u00ednh x\u00e1c \u0111\u1ecbnh th\u1ee9 t\u1ef1 v\u1eadt l\u00fd c\u1ee7a d\u1eef li\u1ec7u tr\u00ean \u0111\u0129a (Ch\u1ec9 m\u1ee5c c\u00f3 c\u1ea5u tr\u00fac). Vi\u1ec7c ch\u1ecdn kh\u00f3a ch\u00ednh tu\u1ea7n t\u1ef1 v\u00e0 ng\u1eafn \u0111\u1ea3m b\u1ea3o d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef li\u1ec1n k\u1ec1 nhau. \u0110i\u1ec1u n\u00e0y gi\u1ea3m thi\u1ec3u ph\u00e2n m\u1ea3nh v\u00e0 cho ph\u00e9p qu\u00e9t ph\u1ea1m vi nhanh h\u01a1n. Ng\u01b0\u1ee3c l\u1ea1i, m\u1ed9t kh\u00f3a ch\u00ednh ng\u1eabu nhi\u00ean v\u00e0 d\u00e0i c\u00f3 th\u1ec3 g\u00e2y ra hi\u1ec7n t\u01b0\u1ee3ng chia trang trong qu\u00e1 tr\u00ecnh ch\u00e8n, l\u00e0m gi\u1ea3m hi\u1ec7u su\u1ea5t ghi v\u00e0 l\u00e0m t\u0103ng chi ph\u00ed l\u01b0u tr\u1eef.<\/p>\n

Nh\u1eefng y\u1ebfu t\u1ed1 quan tr\u1ecdng c\u1ea7n xem x\u00e9t \u0111\u1ed1i v\u1edbi Kh\u00f3a ch\u00ednh<\/h3>\n
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  • T\u00ednh tu\u1ea7n t\u1ef1:<\/strong>C\u00e1c s\u1ed1 nguy\u00ean t\u1ef1 t\u0103ng th\u01b0\u1eddng \u0111\u01b0\u1ee3c \u01b0u ti\u00ean cho c\u00e1c t\u00e1c v\u1ee5 ghi d\u1eef li\u1ec7u n\u1eb7ng.<\/li>\n
  • K\u00edch th\u01b0\u1edbc:<\/strong>Kh\u00f3a nh\u1ecf h\u01a1n l\u00e0m gi\u1ea3m k\u00edch th\u01b0\u1edbc c\u1ee7a c\u00e1c ch\u1ec9 m\u1ee5c ph\u1ee5, v\u00ec ch\u00fang \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef d\u01b0\u1edbi d\u1ea1ng con tr\u1ecf trong c\u00e1c ch\u1ec9 m\u1ee5c \u0111\u00f3.<\/li>\n
  • T\u00ednh \u1ed5n \u0111\u1ecbnh:<\/strong>Kh\u00f3a ch\u00ednh kh\u00f4ng n\u00ean thay \u0111\u1ed5i. C\u1eadp nh\u1eadt kh\u00f3a ch\u00ednh th\u01b0\u1eddng \u0111\u00f2i h\u1ecfi c\u1eadp nh\u1eadt t\u1ea5t c\u1ea3 c\u00e1c kh\u00f3a ngo\u1ea1i li\u00ean quan.<\/li>\n<\/ul>\n

    2. Chu\u1ea9n h\u00f3a so v\u1edbi C\u00e1c Th\u1ecfa hi\u1ec7p Hi\u1ec7u su\u1ea5t \u2696\ufe0f<\/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. M\u1eb7c d\u00f9 th\u01b0\u1eddng \u0111\u01b0\u1ee3c li\u00ean k\u1ebft v\u1edbi ch\u1ea5t l\u01b0\u1ee3ng d\u1eef li\u1ec7u, n\u00f3 c\u00f3 \u1ea3nh h\u01b0\u1edfng s\u00e2u s\u1eafc \u0111\u1ebfn hi\u1ec7u su\u1ea5t. M\u1ed9t l\u01b0\u1ee3c \u0111\u1ed3 \u0111\u01b0\u1ee3c chu\u1ea9n h\u00f3a cao (v\u00ed d\u1ee5: d\u1ea1ng chu\u1ea9n h\u00f3a th\u1ee9 ba) th\u01b0\u1eddng y\u00eau c\u1ea7u nhi\u1ec1u thao t\u00e1c n\u1ed1i h\u01a1n \u0111\u1ec3 ph\u1ee5c h\u1ed3i d\u1eef li\u1ec7u, trong khi l\u01b0\u1ee3c \u0111\u1ed3 kh\u00f4ng chu\u1ea9n h\u00f3a gi\u1ea3m s\u1ed1 thao t\u00e1c n\u1ed1i nh\u01b0ng l\u1ea1i l\u00e0m t\u0103ng \u0111\u1ed9 ph\u1ee9c t\u1ea1p v\u1ec1 l\u01b0u tr\u1eef v\u00e0 c\u1eadp nh\u1eadt.<\/p>\n

    Vi\u1ec7c quy\u1ebft \u0111\u1ecbnh chu\u1ea9n h\u00f3a hay kh\u00f4ng chu\u1ea9n h\u00f3a l\u00e0 m\u1ed9t s\u1ef1 c\u00e2n b\u1eb1ng gi\u1eefa t\u1ed1c \u0111\u1ed9 \u0111\u1ecdc v\u00e0 t\u1ed1c \u0111\u1ed9 ghi. Trong m\u00f4i tr\u01b0\u1eddng \u0111\u1ecdc d\u1eef li\u1ec7u n\u1eb7ng, vi\u1ec7c kh\u00f4ng chu\u1ea9n h\u00f3a c\u00f3 th\u1ec3 gi\u1ea3m \u0111\u00e1ng k\u1ec3 th\u1eddi gian truy v\u1ea5n b\u1eb1ng c\u00e1ch tr\u00e1nh c\u00e1c thao t\u00e1c n\u1ed1i ph\u1ee9c t\u1ea1p. Trong m\u00f4i tr\u01b0\u1eddng ghi d\u1eef li\u1ec7u n\u1eb7ng, chu\u1ea9n h\u00f3a gi\u00fap gi\u1ea3m s\u1ed1 l\u01b0\u1ee3ng h\u00e0ng c\u1ea7n c\u1eadp nh\u1eadt tr\u00ean nhi\u1ec1u b\u1ea3ng.<\/p>\n

    Ph\u00e2n t\u00edch T\u00e1c \u0111\u1ed9ng c\u1ee7a Chu\u1ea9n h\u00f3a<\/h3>\n\n\n\n\n\n\n
    Kh\u00eda c\u1ea1nh<\/strong><\/th>\nChu\u1ea9n h\u00f3a cao<\/strong><\/th>\nKh\u00f4ng chu\u1ea9n h\u00f3a<\/strong><\/th>\n<\/tr>\n
    Hi\u1ec7u su\u1ea5t \u0111\u1ecdc<\/td>\nTh\u1ea5p h\u01a1n (Y\u00eau c\u1ea7u n\u1ed1i)<\/td>\nCao h\u01a1n (Truy c\u1eadp b\u1ea3ng \u0111\u01a1n)<\/td>\n<\/tr>\n
    Hi\u1ec7u su\u1ea5t ghi<\/td>\nCao h\u01a1n (\u00cdt tr\u00f9ng l\u1eb7p h\u01a1n)<\/td>\nTh\u1ea5p h\u01a1n (C\u1eadp nh\u1eadt nhi\u1ec1u b\u1ea3n sao)<\/td>\n<\/tr>\n
    T\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u<\/td>\nCao (Ngu\u1ed3n duy nh\u1ea5t c\u1ee7a s\u1ef1 th\u1eadt)<\/td>\nTh\u1ea5p h\u01a1n (Nguy c\u01a1 b\u1ea5t nh\u1ea5t)<\/td>\n<\/tr>\n
    S\u1eed d\u1ee5ng l\u01b0u tr\u1eef<\/td>\nTh\u1ea5p h\u01a1n<\/td>\nCao h\u01a1n<\/td>\n<\/tr>\n<\/table>\n

    3. Kh\u00f3a ngo\u1ea1i v\u00e0 chi ph\u00ed b\u1ea3o to\u00e0n t\u00ednh to\u00e0n v\u1eb9n \ud83d\udd17<\/h2>\n

    Kh\u00f3a ngo\u1ea1i \u0111\u1ea3m b\u1ea3o t\u00ednh to\u00e0n v\u1eb9n tham chi\u1ebfu. Ch\u00fang \u0111\u1ea3m b\u1ea3o r\u1eb1ng m\u1ed9t gi\u00e1 tr\u1ecb trong m\u1ed9t b\u1ea3ng kh\u1edbp v\u1edbi m\u1ed9t gi\u00e1 tr\u1ecb trong b\u1ea3ng kh\u00e1c. M\u1eb7c d\u00f9 \u0111i\u1ec1u n\u00e0y ng\u0103n ch\u1eb7n c\u00e1c b\u1ea3n ghi b\u1ecb t\u00e1ch r\u1eddi, nh\u01b0ng n\u00f3 t\u1ea1o ra chi ph\u00ed x\u1eed l\u00fd t\u1ea1i th\u1eddi \u0111i\u1ec3m ch\u1ea1y. Khi b\u1ea1n ch\u00e8n, c\u1eadp nh\u1eadt ho\u1eb7c x\u00f3a m\u1ed9t h\u00e0ng, c\u01a1 s\u1edf d\u1eef li\u1ec7u ph\u1ea3i ki\u1ec3m tra r\u00e0ng bu\u1ed9c kh\u00f3a ngo\u1ea1i.<\/p>\n

    Vi\u1ec7c ki\u1ec3m tra n\u00e0y kh\u00f4ng mi\u1ec5n ph\u00ed. B\u1ed9 x\u1eed l\u00fd ph\u1ea3i t\u00ecm ki\u1ebfm h\u00e0ng tham chi\u1ebfu v\u00e0 x\u00e1c minh s\u1ef1 t\u1ed3n t\u1ea1i c\u1ee7a n\u00f3. N\u1ebfu b\u1ea3ng tham chi\u1ebfu l\u1edbn v\u00e0 kh\u00f4ng c\u00f3 ch\u1ec9 m\u1ee5c tr\u00ean c\u1ed9t kh\u00f3a ngo\u1ea1i, vi\u1ec7c ki\u1ec3m tra s\u1ebd tr\u1edf th\u00e0nh qu\u00e9t to\u00e0n b\u1ed9 b\u1ea3ng. H\u01a1n n\u1eefa, vi\u1ec7c x\u00f3a m\u1ed9t b\u1ea3n ghi cha \u0111\u00f2i h\u1ecfi b\u1ed9 x\u1eed l\u00fd ph\u1ea3i ki\u1ec3m tra t\u1ea5t c\u1ea3 c\u00e1c b\u1ea3n ghi con \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o kh\u00f4ng c\u00f2n tham chi\u1ebfu n\u00e0o t\u1ed3n t\u1ea1i, c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn vi\u1ec7c kh\u00f3a nhi\u1ec1u h\u00e0ng.<\/p>\n

    Khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng kh\u00f3a ngo\u1ea1i<\/h3>\n
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    • To\u00e0n v\u1eb9n d\u1eef li\u1ec7u quan tr\u1ecdng:<\/strong> N\u1ebfu t\u00ednh ch\u00ednh x\u00e1c c\u1ee7a d\u1eef li\u1ec7u l\u00e0 \u01b0u ti\u00ean h\u00e0ng \u0111\u1ea7u (v\u00ed d\u1ee5: giao d\u1ecbch t\u00e0i ch\u00ednh), h\u00e3y s\u1eed d\u1ee5ng kh\u00f3a ngo\u1ea1i.<\/li>\n
    • Logic \u1ee9ng d\u1ee5ng:<\/strong> N\u1ebfu logic \u1ee9ng d\u1ee5ng ph\u1ee9c t\u1ea1p, giao tr\u00e1ch nhi\u1ec7m to\u00e0n v\u1eb9n cho c\u01a1 s\u1edf d\u1eef li\u1ec7u s\u1ebd gi\u00fap \u0111\u01a1n gi\u1ea3n h\u00f3a m\u00e3 ngu\u1ed3n.<\/li>\n
    • D\u1eef li\u1ec7u nh\u1ecf:<\/strong> Chi ph\u00ed ph\u00e1t sinh l\u00e0 kh\u00f4ng \u0111\u00e1ng k\u1ec3 tr\u00ean c\u00e1c b\u1ea3ng nh\u1ecf.<\/li>\n<\/ul>\n

      Khi n\u00e0o n\u00ean tr\u00e1nh s\u1eed d\u1ee5ng kh\u00f3a ngo\u1ea1i<\/h3>\n
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      • T\u1ed1c \u0111\u1ed9 ghi cao:<\/strong> Lo\u1ea1i b\u1ecf c\u00e1c r\u00e0ng bu\u1ed9c c\u00f3 th\u1ec3 gi\u1ea3m thi\u1ec3u xung \u0111\u1ed9t kh\u00f3a.<\/li>\n
      • Ph\u00e2n t\u00edch quy m\u00f4 l\u1edbn:<\/strong> Trong kho d\u1eef li\u1ec7u, hi\u1ec7u su\u1ea5t th\u01b0\u1eddng quan tr\u1ecdng h\u01a1n t\u00ednh to\u00e0n v\u1eb9n nghi\u00eam ng\u1eb7t.<\/li>\n
      • C\u00e1c l\u1edbp ki\u1ebfn tr\u00fac:<\/strong> Trong c\u00e1c d\u1ecbch v\u1ee5 vi m\u00f4, vi\u1ec7c duy tr\u00ec kh\u00f3a ngo\u1ea1i qua c\u00e1c ranh gi\u1edbi d\u1ecbch v\u1ee5 th\u01b0\u1eddng kh\u00f4ng th\u1ef1c t\u1ebf.<\/li>\n<\/ul>\n

        4. Chi\u1ebfn l\u01b0\u1ee3c ch\u1ec9 m\u1ee5c v\u00e0 ki\u1ec3u d\u1eef li\u1ec7u c\u1ed9t \ud83d\udcd1<\/h2>\n

        M\u1ed9t s\u01a1 \u0111\u1ed3 ERD x\u00e1c \u0111\u1ecbnh ki\u1ec3u d\u1eef li\u1ec7u cho m\u1ed7i c\u1ed9t. Vi\u1ec7c l\u1ef1a ch\u1ecdn gi\u1eefa VARCHAR v\u00e0 CHAR, ho\u1eb7c INT v\u00e0 BIGINT, \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn c\u00e1ch d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef v\u00e0 ch\u1ec9 m\u1ee5c h\u00f3a. C\u00e1c ki\u1ec3u d\u1eef li\u1ec7u nh\u1ecf h\u01a1n ti\u00eau th\u1ee5 \u00edt b\u1ed9 nh\u1edb v\u00e0 kh\u00f4ng gian \u0111\u0129a h\u01a1n, cho ph\u00e9p nhi\u1ec1u d\u1eef li\u1ec7u h\u01a1n \u0111\u01b0\u1ee3c l\u01b0u trong b\u1ed9 \u0111\u1ec7m (RAM).<\/p>\n

        Khi m\u1ed9t truy v\u1ea5n l\u1ecdc theo m\u1ed9t c\u1ed9t, b\u1ed9 x\u1eed l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u ph\u1ee5 thu\u1ed9c v\u00e0o ch\u1ec9 m\u1ee5c \u0111\u1ec3 t\u00ecm h\u00e0ng nhanh ch\u00f3ng. N\u1ebfu thi\u1ebft k\u1ebf l\u01b0\u1ee3c \u0111\u1ed3 kh\u00f4ng ph\u00f9 h\u1ee3p v\u1edbi m\u1eabu truy v\u1ea5n, c\u00e1c ch\u1ec9 m\u1ee5c s\u1ebd tr\u1edf n\u00ean v\u00f4 d\u1ee5ng. V\u00ed d\u1ee5, vi\u1ec7c t\u1ea1o ch\u1ec9 m\u1ee5c tr\u00ean m\u1ed9t c\u1ed9t hi\u1ebfm khi \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng trong c\u00e1c m\u1ec7nh \u0111\u1ec1 WHERE l\u00e0 l\u00e3ng ph\u00ed t\u00e0i nguy\u00ean.<\/p>\n

        T\u1ed1i \u01b0u h\u00f3a ki\u1ec3u c\u1ed9t<\/h3>\n
          \n
        • C\u1ed1 \u0111\u1ecbnh so v\u1edbi \u0111\u1ed9 d\u00e0i bi\u1ebfn \u0111\u1ed5i:<\/strong> S\u1eed d\u1ee5ng CHAR cho d\u1eef li\u1ec7u c\u00f3 \u0111\u1ed9 d\u00e0i c\u1ed1 \u0111\u1ecbnh (v\u00ed d\u1ee5: m\u00e3 qu\u1ed1c gia) \u0111\u1ec3 gi\u1ea3m ph\u00e2n m\u1ea3nh. S\u1eed d\u1ee5ng VARCHAR cho d\u1eef li\u1ec7u c\u00f3 \u0111\u1ed9 d\u00e0i thay \u0111\u1ed5i.<\/li>\n
        • Ph\u1ea1m vi s\u1ed1 nguy\u00ean:<\/strong> Kh\u00f4ng s\u1eed d\u1ee5ng BIGINT n\u1ebfu INT l\u00e0 \u0111\u1ee7. C\u00e1c s\u1ed1 nguy\u00ean nh\u1ecf h\u01a1n s\u1ebd ch\u1ee9a \u0111\u01b0\u1ee3c nhi\u1ec1u h\u00e0ng h\u01a1n m\u1ed7i trang.<\/li>\n
        • Bi\u1ec3u di\u1ec5n ki\u1ec3u logic:<\/strong> S\u1eed d\u1ee5ng ki\u1ec3u TINYINT(1) ho\u1eb7c BOOLEAN thay v\u00ec l\u01b0u tr\u1eef chu\u1ed7i ‘C\u00f3’\/’Kh\u00f4ng’.<\/li>\n<\/ul>\n

          5. H\u1eadu qu\u1ea3 c\u1ee7a t\u00ednh ch\u1ea5t cardinality m\u1ed1i quan h\u1ec7 \ud83d\udcca<\/h2>\n

          S\u1ed1 l\u01b0\u1ee3ng quan h\u1ec7 (m\u1ed9t-\u0111\u1ed1i-m\u1ed9t, m\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u, nhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u) x\u00e1c \u0111\u1ecbnh c\u00e1ch d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c li\u00ean k\u1ebft. M\u1ed7i lo\u1ea1i quan h\u1ec7 c\u00f3 \u0111\u1eb7c \u0111i\u1ec3m hi\u1ec7u su\u1ea5t kh\u00e1c nhau.<\/p>\n

          M\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u (1:N)<\/h3>\n

          \u0110\u00e2y l\u00e0 m\u1ed1i quan h\u1ec7 ph\u1ed5 bi\u1ebfn nh\u1ea5t. B\u1ea3ng cha l\u01b0u m\u1ed9t b\u1ea3n ghi, c\u00f2n b\u1ea3ng con l\u01b0u nhi\u1ec1u b\u1ea3n ghi. Hi\u1ec7u su\u1ea5t ph\u1ee5 thu\u1ed9c r\u1ea5t nhi\u1ec1u v\u00e0o ch\u1ec9 m\u1ee5c tr\u00ean c\u1ed9t kh\u00f3a ngo\u1ea1i trong b\u1ea3ng con. Kh\u00f4ng c\u00f3 ch\u1ec9 m\u1ee5c n\u00e0y, vi\u1ec7c t\u00ecm t\u1ea5t c\u1ea3 c\u00e1c b\u1ea3n ghi con cho m\u1ed9t b\u1ea3n ghi cha \u0111\u00f2i h\u1ecfi ph\u1ea3i qu\u00e9t to\u00e0n b\u1ed9 b\u1ea3ng con.<\/p>\n

          Nhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u (N:M)<\/h3>\n

          \u0110i\u1ec1u n\u00e0y y\u00eau c\u1ea7u m\u1ed9t b\u1ea3ng li\u00ean k\u1ebft (\u0111\u01a1n v\u1ecb li\u00ean k\u1ebft). \u0110i\u1ec1u n\u00e0y th\u00eam m\u1ed9t l\u1edbp trung gian. C\u00e1c truy v\u1ea5n li\u00ean quan \u0111\u1ebfn m\u1ed1i quan h\u1ec7 N:M th\u01b0\u1eddng y\u00eau c\u1ea7u ba ph\u00e9p n\u1ed1i: B\u1ea3ng A, B\u1ea3ng li\u00ean k\u1ebft, B\u1ea3ng B. S\u1ef1 ph\u1ee9c t\u1ea1p n\u00e0y l\u00e0m t\u0103ng s\u1eed d\u1ee5ng CPU v\u00e0 y\u00eau c\u1ea7u b\u1ed9 nh\u1edb.<\/p>\n

          M\u1ed9t-\u0111\u1ed1i-m\u1ed9t (1:1)<\/h3>\n

          Th\u01b0\u1eddng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 chia m\u1ed9t b\u1ea3ng l\u1edbn th\u00e0nh c\u00e1c nh\u00f3m logic. \u0110i\u1ec1u n\u00e0y c\u00f3 th\u1ec3 c\u1ea3i thi\u1ec7n hi\u1ec7u su\u1ea5t n\u1ebfu ch\u1ec9 m\u1ed9t t\u1eadp h\u1ee3p con c\u00e1c c\u1ed9t \u0111\u01b0\u1ee3c truy v\u1ea5n th\u01b0\u1eddng xuy\u00ean. Tuy nhi\u00ean, \u0111i\u1ec1u n\u00e0y l\u00e0m t\u0103ng chi ph\u00ed c\u1ee7a ph\u00e9p n\u1ed1i \u0111\u1ec3 l\u1ea5y to\u00e0n b\u1ed9 b\u1ea3n ghi.<\/p>\n

          6. Xem x\u00e9t v\u1ec1 ph\u00e2n v\u00f9ng v\u00e0 chia nh\u1ecf d\u1eef li\u1ec7u \ud83d\uddc3\ufe0f<\/h2>\n

          Khi d\u1eef li\u1ec7u t\u0103ng l\u00ean, m\u1ed9t b\u1ea3ng duy nh\u1ea5t c\u00f3 th\u1ec3 tr\u1edf n\u00ean qu\u00e1 l\u1edbn \u0111\u1ec3 qu\u1ea3n l\u00fd hi\u1ec7u qu\u1ea3. Ph\u00e2n v\u00f9ng cho ph\u00e9p b\u1ea1n chia m\u1ed9t b\u1ea3ng l\u1edbn th\u00e0nh c\u00e1c ph\u1ea7n nh\u1ecf h\u01a1n, d\u1ec5 qu\u1ea3n l\u00fd h\u01a1n d\u1ef1a tr\u00ean m\u1ed9t kh\u00f3a (v\u00ed d\u1ee5: ng\u00e0y th\u00e1ng). Thi\u1ebft k\u1ebf ERD ph\u1ea3i d\u1ef1 ki\u1ebfn \u0111i\u1ec1u n\u00e0y.<\/p>\n

          N\u1ebfu b\u1ea1n thi\u1ebft k\u1ebf m\u1ed9t l\u01b0\u1ee3c \u0111\u1ed3 cho h\u1ec7 th\u1ed1ng s\u1ebd \u0111\u01b0\u1ee3c chia nh\u1ecf (chia tr\u00ean nhi\u1ec1u m\u00e1y ch\u1ee7), kh\u00f3a ph\u00e2n v\u00f9ng ph\u1ea3i \u0111\u01b0\u1ee3c ch\u1ecdn c\u1ea9n th\u1eadn. Kh\u00f3a n\u00e0y n\u00ean \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng th\u01b0\u1eddng xuy\u00ean trong c\u00e1c truy v\u1ea5n \u0111\u1ec3 cho ph\u00e9p h\u1ec7 th\u1ed1ng \u0111\u1ecbnh tuy\u1ebfn y\u00eau c\u1ea7u \u0111\u1ebfn m\u1ea3nh d\u1eef li\u1ec7u \u0111\u00fang. Vi\u1ec7c ch\u1ecdn m\u1ed9t kh\u00f3a kh\u00f4ng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng trong truy v\u1ea5n bu\u1ed9c h\u1ec7 th\u1ed1ng ph\u1ea3i t\u1ed5ng h\u1ee3p d\u1eef li\u1ec7u t\u1eeb t\u1ea5t c\u1ea3 c\u00e1c m\u1ea3nh, \u0111i\u1ec1u n\u00e0y r\u1ea5t ch\u1eadm.<\/p>\n

          Chi\u1ebfn l\u01b0\u1ee3c ph\u00e2n v\u00f9ng<\/h3>\n
            \n
          • Ph\u00e2n v\u00f9ng theo kho\u1ea3ng:<\/strong> Chia theo kho\u1ea3ng ng\u00e0y ho\u1eb7c ID. Ph\u00f9 h\u1ee3p v\u1edbi d\u1eef li\u1ec7u chu\u1ed7i th\u1eddi gian.<\/li>\n
          • Ph\u00e2n v\u00f9ng theo danh s\u00e1ch:<\/strong> Chia theo c\u00e1c gi\u00e1 tr\u1ecb c\u1ee5 th\u1ec3 (v\u00ed d\u1ee5: m\u00e3 khu v\u1ef1c).<\/li>\n
          • Ph\u00e2n v\u00f9ng theo b\u0103m:<\/strong> Ph\u00e2n ph\u1ed1i d\u1eef li\u1ec7u \u0111\u1ec1u \u0111\u1ec3 tr\u00e1nh c\u00e1c \u0111i\u1ec3m n\u00f3ng.<\/li>\n<\/ul>\n

            7. Nh\u1eefng sai l\u1ea7m ph\u1ed5 bi\u1ebfn trong thi\u1ebft k\u1ebf \ud83d\udeab<\/h2>\n

            Ngay c\u1ea3 c\u00e1c ki\u1ebfn tr\u00fac s\u01b0 c\u00f3 kinh nghi\u1ec7m c\u0169ng c\u00f3 th\u1ec3 t\u1ea1o ra c\u00e1c \u0111i\u1ec3m ngh\u1ebdn hi\u1ec7u su\u1ea5t th\u00f4ng qua c\u00e1c l\u1ef1a ch\u1ecdn thi\u1ebft k\u1ebf. Nh\u1eadn di\u1ec7n nh\u1eefng m\u1eabu n\u00e0y s\u1edbm s\u1ebd ng\u0103n ng\u1eeba vi\u1ec7c t\u00e1i c\u1ea5u tr\u00fac t\u1ed1n k\u00e9m v\u1ec1 sau.<\/p>\n

              \n
            • Qu\u00e1 chu\u1ea9n h\u00f3a:<\/strong> Chia d\u1eef li\u1ec7u th\u00e0nh qu\u00e1 nhi\u1ec1u b\u1ea3ng nh\u1ecf l\u00e0m t\u0103ng \u0111\u1ed9 ph\u1ee9c t\u1ea1p c\u1ee7a ph\u00e9p n\u1ed1i v\u00e0 gi\u1ea3m hi\u1ec7u qu\u1ea3 b\u1ed9 nh\u1edb \u0111\u1ec7m.<\/li>\n
            • B\u1ecf qua \u0111\u1ed9 ch\u1ecdn l\u1ecdc:<\/strong>Ch\u1ec9 m\u1ee5c h\u00f3a c\u00e1c c\u1ed9t c\u00f3 \u0111\u1ed9 ch\u1ecdn l\u1ecdc th\u1ea5p (v\u00ed d\u1ee5: gi\u1edbi t\u00ednh ho\u1eb7c c\u1edd tr\u1ea1ng th\u00e1i) th\u01b0\u1eddng d\u1eabn \u0111\u1ebfn hi\u1ec7u su\u1ea5t k\u00e9m v\u00ec tr\u00ecnh t\u1ed1i \u01b0u c\u00f3 th\u1ec3 b\u1ecf qua ch\u1ec9 m\u1ee5c v\u00e0 qu\u00e9t to\u00e0n b\u1ed9 b\u1ea3ng d\u00f9 sao c\u0169ng.<\/li>\n
            • Chuy\u1ec3n \u0111\u1ed5i ng\u1ea7m:<\/strong>Thi\u1ebft k\u1ebf m\u1ed9t c\u1ed9t d\u01b0\u1edbi d\u1ea1ng chu\u1ed7i khi gi\u00e1 tr\u1ecb s\u1ed1 \u0111\u01b0\u1ee3c mong \u0111\u1ee3i bu\u1ed9c h\u1ec7 th\u1ed1ng ph\u1ea3i chuy\u1ec3n \u0111\u1ed5i ki\u1ec3u d\u1eef li\u1ec7u trong c\u00e1c truy v\u1ea5n, ng\u0103n c\u1ea3n vi\u1ec7c s\u1eed d\u1ee5ng ch\u1ec9 m\u1ee5c.<\/li>\n
            • M\u1eabu truy v\u1ea5n N+1:<\/strong>Thi\u1ebft k\u1ebf c\u00e1c m\u1ed1i quan h\u1ec7 khuy\u1ebfn kh\u00edch vi\u1ec7c l\u1ea5y d\u1eef li\u1ec7u theo v\u00f2ng l\u1eb7p thay v\u00ec c\u00e1c ph\u00e9p n\u1ed1i theo nh\u00f3m c\u00f3 th\u1ec3 l\u00e0m qu\u00e1 t\u1ea3i m\u00e1y ch\u1ee7.<\/li>\n<\/ul>\n

              8. B\u1ea3o v\u1ec7 cho t\u01b0\u01a1ng lai v\u00e0 s\u1ef1 ph\u00e1t tri\u1ec3n \ud83d\udee1\ufe0f<\/h2>\n

              C\u01a1 s\u1edf d\u1eef li\u1ec7u ph\u00e1t tri\u1ec3n theo th\u1eddi gian. Y\u00eau c\u1ea7u thay \u0111\u1ed5i, v\u00e0 c\u00e1c t\u00ednh n\u0103ng m\u1edbi \u0111\u01b0\u1ee3c th\u00eam v\u00e0o. M\u1ed9t l\u01b0\u1ee3c \u0111\u1ed3 hi\u1ec7u qu\u1ea3 h\u00f4m nay c\u00f3 th\u1ec3 tr\u1edf th\u00e0nh \u0111i\u1ec3m ngh\u1ebdn v\u00e0o ng\u00e0y mai n\u1ebfu thi\u1ebfu t\u00ednh linh ho\u1ea1t. ERD n\u00ean h\u1ed7 tr\u1ee3 s\u1ef1 ph\u00e1t tri\u1ec3n m\u00e0 kh\u00f4ng c\u1ea7n ph\u1ea3i vi\u1ebft l\u1ea1i ho\u00e0n to\u00e0n.<\/p>\n

              C\u00e2n nh\u1eafc th\u00eam c\u00e1c c\u1ed9t c\u00f3 kh\u1ea3 n\u0103ng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 l\u1ecdc trong t\u01b0\u01a1ng lai. M\u1eb7c d\u00f9 \u0111i\u1ec1u n\u00e0y l\u00e0m t\u0103ng k\u00edch th\u01b0\u1edbc b\u1ea3n ghi m\u1ed9t ch\u00fat, nh\u01b0ng s\u1ebd ti\u1ebft ki\u1ec7m chi ph\u00ed thay \u0111\u1ed5i c\u1ea5u tr\u00fac b\u1ea3ng v\u1ec1 sau, \u0111i\u1ec1u n\u00e0y c\u00f3 th\u1ec3 l\u00e0 thao t\u00e1c t\u1ed1n k\u00e9m tr\u00ean d\u1eef li\u1ec7u l\u1edbn. Ngo\u00e0i ra, h\u00e3y c\u00e2n nh\u1eafc t\u00e1c \u0111\u1ed9ng c\u1ee7a vi\u1ec7c th\u00eam ch\u1ec9 m\u1ee5c m\u1edbi. M\u1ed7i ch\u1ec9 m\u1ee5c \u0111\u1ec1u ti\u00eau t\u1ed1n t\u00e0i nguy\u00ean ghi. Thi\u1ebft k\u1ebf l\u01b0\u1ee3c \u0111\u1ed3 \u0111\u1ec3 t\u1ed1i thi\u1ec3u h\u00f3a s\u1ed1 l\u01b0\u1ee3ng ch\u1ec9 m\u1ee5c c\u1ea7n thi\u1ebft.<\/p>\n

              B\u1ea3ng ki\u1ec3m thi\u1ebft k\u1ebf cho hi\u1ec7u su\u1ea5t<\/h3>\n
                \n
              • C\u00e1c kh\u00f3a ch\u00ednh c\u00f3 ng\u1eafn v\u00e0 tu\u1ea7n t\u1ef1 kh\u00f4ng?<\/li>\n
              • C\u00e1c kh\u00f3a ngo\u1ea1i c\u00f3 \u0111\u01b0\u1ee3c ch\u1ec9 m\u1ee5c h\u00f3a kh\u00f4ng?<\/li>\n
              • C\u00e1c ki\u1ec3u d\u1eef li\u1ec7u c\u00f3 ph\u1ea3i l\u00e0 ki\u1ec3u h\u1ee3p l\u1ec7 nh\u1ecf nh\u1ea5t c\u00f3 th\u1ec3 kh\u00f4ng?<\/li>\n
              • C\u00e1c b\u1ed9 l\u1ecdc th\u01b0\u1eddng xuy\u00ean c\u00f3 \u0111\u01b0\u1ee3c bao ph\u1ee7 b\u1edfi ch\u1ec9 m\u1ee5c kh\u00f4ng?<\/li>\n
              • M\u1ee9c \u0111\u1ed9 chu\u1ea9n h\u00f3a c\u00f3 ph\u00f9 h\u1ee3p v\u1edbi kh\u1ed1i l\u01b0\u1ee3ng c\u00f4ng vi\u1ec7c kh\u00f4ng?<\/li>\n
              • B\u1ea1n \u0111\u00e3 c\u00e2n nh\u1eafc vi\u1ec7c chia t\u00e1ch cho c\u00e1c b\u1ea3ng l\u1edbn ch\u01b0a?<\/li>\n
              • C\u00f3 c\u1ed9t n\u00e0o l\u01b0u tr\u1eef JSON ho\u1eb7c v\u0103n b\u1ea3n ph\u1ee9c t\u1ea1p c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c c\u1ea5u tr\u00fac l\u1ea1i kh\u00f4ng?<\/li>\n<\/ul>\n

                9. Vai tr\u00f2 c\u1ee7a k\u1ebf ho\u1ea1ch th\u1ef1c thi \ud83d\udccb<\/h2>\n

                Cu\u1ed1i c\u00f9ng, b\u1ed9 \u0111\u1ed9ng c\u01a1 c\u01a1 s\u1edf d\u1eef li\u1ec7u quy\u1ebft \u0111\u1ecbnh c\u00e1ch th\u1ef1c thi m\u1ed9t truy v\u1ea5n d\u1ef1a tr\u00ean l\u01b0\u1ee3c \u0111\u1ed3 v\u00e0 th\u1ed1ng k\u00ea. ERD \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn th\u1ed1ng k\u00ea m\u00e0 b\u1ed9 \u0111\u1ed9ng c\u01a1 thu th\u1eadp. V\u00ed d\u1ee5, m\u1ed9t c\u1ed9t c\u00f3 ph\u00e2n b\u1ed1 gi\u00e1 tr\u1ecb kh\u00e1c nhau s\u1ebd \u0111\u01b0\u1ee3c x\u1eed l\u00fd kh\u00e1c bi\u1ec7t so v\u1edbi m\u1ed9t c\u1ed9t c\u00f3 d\u1eef li\u1ec7u l\u1ec7ch. Hi\u1ec3u c\u00e1ch ho\u1ea1t \u0111\u1ed9ng c\u1ee7a k\u1ebf ho\u1ea1ch th\u1ef1c thi gi\u00fap b\u1ea1n gi\u1ea3i th\u00edch l\u00fd do t\u1ea1i sao m\u1ed9t truy v\u1ea5n ch\u1ea1y ch\u1eadm.<\/p>\n

                N\u1ebfu m\u1ed9t truy v\u1ea5n th\u1ef1c hi\u1ec7n qu\u00e9t to\u00e0n b\u1ed9 b\u1ea3ng, \u0111i\u1ec1u n\u00e0y th\u01b0\u1eddng cho th\u1ea5y thi\u1ebfu ch\u1ec9 m\u1ee5c ho\u1eb7c thi\u1ebft k\u1ebf kh\u00f4ng h\u1ed7 tr\u1ee3 l\u1ecdc hi\u1ec7u qu\u1ea3. N\u1ebfu n\u00f3 th\u1ef1c hi\u1ec7n nhi\u1ec1u v\u00f2ng l\u1eb7p l\u1ed3ng nhau, \u0111i\u1ec1u \u0111\u00f3 cho th\u1ea5y c\u00e1c ph\u00e9p n\u1ed1i ph\u1ee9c t\u1ea1p c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c \u0111\u01a1n gi\u1ea3n h\u00f3a. B\u1eb1ng c\u00e1ch \u0111\u1ed3ng b\u1ed9 h\u00f3a ERD v\u1edbi c\u00e1c m\u1eabu truy c\u1eadp mong \u0111\u1ee3i, b\u1ea1n \u0111\u1ecbnh h\u01b0\u1edbng b\u1ed9 \u0111\u1ed9ng c\u01a1 \u0111\u1ebfn c\u00e1c k\u1ebf ho\u1ea1ch th\u1ef1c thi t\u1ed1i \u01b0u.<\/p>\n

                10. C\u00e2n b\u1eb1ng gi\u1eefa t\u00ednh to\u00e0n v\u1eb9n v\u00e0 t\u1ed1c \u0111\u1ed9 \u2696\ufe0f<\/h2>\n

                Kh\u00f4ng c\u00f3 l\u01b0\u1ee3c \u0111\u1ed3 ho\u00e0n h\u1ea3o n\u00e0o. M\u1ed7i l\u1ef1a ch\u1ecdn thi\u1ebft k\u1ebf \u0111\u1ec1u \u0111i k\u00e8m v\u1edbi s\u1ef1 \u0111\u00e1nh \u0111\u1ed5i. M\u1ee5c ti\u00eau kh\u00f4ng ph\u1ea3i l\u00e0 lo\u1ea1i b\u1ecf ho\u00e0n to\u00e0n c\u00e1c v\u1ea5n \u0111\u1ec1 hi\u1ec7u su\u1ea5t m\u00e0 l\u00e0 qu\u1ea3n l\u00fd ch\u00fang m\u1ed9t c\u00e1ch chi\u1ebfn l\u01b0\u1ee3c. Trong m\u1ed9t s\u1ed1 tr\u01b0\u1eddng h\u1ee3p, ch\u1ea5p nh\u1eadn r\u1ee7i ro nh\u1ecf v\u1ec1 s\u1ef1 kh\u00f4ng nh\u1ea5t qu\u00e1n d\u1eef li\u1ec7u (th\u00f4ng qua ki\u1ec3m tra \u1edf c\u1ea5p \u0111\u1ed9 \u1ee9ng d\u1ee5ng thay v\u00ec r\u00e0ng bu\u1ed9c c\u01a1 s\u1edf d\u1eef li\u1ec7u) l\u00e0 m\u1ed9t \u0111\u00e1nh \u0111\u1ed5i h\u1ee3p l\u00fd \u0111\u1ec3 \u0111\u1ea1t \u0111\u01b0\u1ee3c t\u1ed1c \u0111\u1ed9 ghi c\u1ef1c cao.<\/p>\n

                Th\u01b0\u1eddng xuy\u00ean xem x\u00e9t l\u1ea1i ERD d\u1ef1a tr\u00ean nh\u1eadt k\u00fd truy v\u1ea5n th\u1ef1c t\u1ebf. X\u00e1c \u0111\u1ecbnh c\u00e1c truy v\u1ea5n ch\u1eadm nh\u1ea5t v\u00e0 truy v\u1ebft ch\u00fang tr\u1edf l\u1ea1i l\u01b0\u1ee3c \u0111\u1ed3. V\u00f2ng ph\u1ea3n h\u1ed3i n\u00e0y \u0111\u1ea3m b\u1ea3o thi\u1ebft k\u1ebf c\u1ee7a b\u1ea1n ph\u00e1t tri\u1ec3n song h\u00e0nh v\u1edbi nhu c\u1ea7u c\u1ee7a \u1ee9ng d\u1ee5ng.<\/p>\n

                T\u00f3m t\u1eaft c\u00e1c khu v\u1ef1c \u1ea3nh h\u01b0\u1edfng \ud83d\udcdd<\/h2>\n\n\n\n\n\n\n\n
                Y\u1ebfu t\u1ed1 thi\u1ebft k\u1ebf<\/strong><\/th>\n\u1ea2nh h\u01b0\u1edfng \u0111\u1ebfn hi\u1ec7u su\u1ea5t<\/strong><\/th>\nKhuy\u1ebfn ngh\u1ecb<\/strong><\/th>\n<\/tr>\n
                Lo\u1ea1i kh\u00f3a ch\u00ednh<\/td>\nCao (B\u1ed9 nh\u1edb v\u00e0 ch\u1ec9 m\u1ee5c)<\/td>\nS\u1eed d\u1ee5ng s\u1ed1 nguy\u00ean ho\u1eb7c UUID m\u1ed9t c\u00e1ch nh\u1ea5t qu\u00e1n.<\/td>\n<\/tr>\n
                Kh\u00f3a ngo\u1ea1i<\/td>\nTrung b\u00ecnh (chi ph\u00ed ghi)<\/td>\nCh\u1ec9 m\u1ee5c c\u00e1c c\u1ed9t kh\u00f3a ngo\u1ea1i; lo\u1ea1i b\u1ecf n\u1ebfu t\u00ednh to\u00e0n v\u1eb9n \u0111\u01b0\u1ee3c x\u1eed l\u00fd \u1edf n\u01a1i kh\u00e1c.<\/td>\n<\/tr>\n
                Chu\u1ea9n h\u00f3a<\/td>\nCao (\u0110\u1ed9 ph\u1ee9c t\u1ea1p c\u1ee7a ph\u00e9p n\u1ed1i)<\/td>\nGi\u1ea3m chu\u1ea9n h\u00f3a c\u00e1c b\u1ea3ng c\u00f3 nhi\u1ec1u truy v\u1ea5n \u0111\u1ecdc.<\/td>\n<\/tr>\n
                Ki\u1ec3u d\u1eef li\u1ec7u<\/td>\nTrung b\u00ecnh (s\u1eed d\u1ee5ng b\u1ed9 nh\u1edb)<\/td>\nS\u1eed d\u1ee5ng ki\u1ec3u c\u1ee5 th\u1ec3 nh\u1ea5t c\u00f3 s\u1eb5n.<\/td>\n<\/tr>\n
                S\u1ed1 l\u01b0\u1ee3ng<\/td>\nCao (Chi ph\u00ed n\u1ed1i)<\/td>\nT\u1ed1i \u01b0u h\u00f3a c\u00e1c b\u1ea3ng li\u00ean k\u1ebft cho c\u00e1c m\u1ed1i quan h\u1ec7 N:M.<\/td>\n<\/tr>\n<\/table>\n

                B\u1eb1ng c\u00e1ch coi s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c th\u1ec3 nh\u01b0 m\u1ed9t y\u1ebfu t\u1ed1 hi\u1ec7u su\u1ea5t thay v\u00ec ch\u1ec9 l\u00e0 b\u1ea3n \u0111\u1ed3 logic, b\u1ea1n c\u00f3 th\u1ec3 x\u00e2y d\u1ef1ng c\u00e1c h\u1ec7 th\u1ed1ng b\u1ec1n v\u1eefng, m\u1edf r\u1ed9ng \u0111\u01b0\u1ee3c v\u00e0 hi\u1ec7u qu\u1ea3. Nh\u1eefng quy\u1ebft \u0111\u1ecbnh b\u1ea1n \u0111\u01b0a ra ngay b\u00e2y gi\u1edd s\u1ebd \u0111\u1ecbnh h\u00ecnh h\u00e0nh vi c\u1ee7a \u1ee9ng d\u1ee5ng c\u1ee7a b\u1ea1n trong nhi\u1ec1u n\u0103m t\u1edbi.<\/p>\n","protected":false},"excerpt":{"rendered":"

                M\u00f4 h\u00ecnh h\u00f3a d\u1eef li\u1ec7u th\u01b0\u1eddng \u0111\u01b0\u1ee3c xem nh\u01b0 m\u1ed9t b\u00e0i t\u1eadp t\u0129nh nh\u1eb1m x\u00e1c \u0111\u1ecbnh c\u00e1c m\u1ed1i quan h\u1ec7 v\u00e0 th\u1ef1c th\u1ec3. Tuy nhi\u00ean, s\u01a1 \u0111\u1ed3 quan h\u1ec7 th\u1ef1c…<\/p>\n","protected":false},"author":1,"featured_media":1576,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_yoast_wpseo_title":"ERD v\u00e0 Hi\u1ec7u su\u1ea5t: T\u00e1c \u0111\u1ed9ng \u0111\u1ebfn T\u1ed1c \u0111\u1ed9 truy v\u1ea5n \ud83d\ude80","_yoast_wpseo_metadesc":"H\u1ecdc c\u00e1ch c\u00e1c l\u1ef1a ch\u1ecdn thi\u1ebft k\u1ebf ERD \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn hi\u1ec7u su\u1ea5t c\u01a1 s\u1edf d\u1eef li\u1ec7u. T\u1ed1i \u01b0u h\u00f3a l\u01b0\u1ee3c \u0111\u1ed3 \u0111\u1ec3 truy v\u1ea5n nhanh h\u01a1n m\u00e0 kh\u00f4ng c\u1ea7n c\u00f4ng c\u1ee5 \u0111\u1eb7c th\u00f9 nh\u00e0 cung c\u1ea5p.","fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[88],"tags":[84,87],"class_list":["post-1575","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-erd","tag-academic","tag-erd"],"yoast_head":"\nERD v\u00e0 Hi\u1ec7u su\u1ea5t: T\u00e1c \u0111\u1ed9ng \u0111\u1ebfn T\u1ed1c \u0111\u1ed9 truy v\u1ea5n \ud83d\ude80<\/title>\n<meta name=\"description\" content=\"H\u1ecdc c\u00e1ch c\u00e1c l\u1ef1a ch\u1ecdn thi\u1ebft k\u1ebf ERD \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn hi\u1ec7u su\u1ea5t c\u01a1 s\u1edf d\u1eef li\u1ec7u. T\u1ed1i \u01b0u h\u00f3a l\u01b0\u1ee3c \u0111\u1ed3 \u0111\u1ec3 truy v\u1ea5n nhanh h\u01a1n m\u00e0 kh\u00f4ng c\u1ea7n c\u00f4ng c\u1ee5 \u0111\u1eb7c th\u00f9 nh\u00e0 cung c\u1ea5p.\" \/>\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.viz-read.com\/vi\/erd-performance-query-speed\/\" \/>\n<meta property=\"og:locale\" content=\"vi_VN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"ERD v\u00e0 Hi\u1ec7u su\u1ea5t: T\u00e1c \u0111\u1ed9ng \u0111\u1ebfn T\u1ed1c \u0111\u1ed9 truy v\u1ea5n \ud83d\ude80\" \/>\n<meta property=\"og:description\" content=\"H\u1ecdc c\u00e1ch c\u00e1c l\u1ef1a ch\u1ecdn thi\u1ebft k\u1ebf ERD \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn hi\u1ec7u su\u1ea5t c\u01a1 s\u1edf d\u1eef li\u1ec7u. 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