![\"Cute](\"https:\/\/www.we-notes.com\/wp-content\/uploads\/2026\/04\/kawaii-er-diagram-attributes-infographic.jpg\"\/)
<\/figure>\n<\/div>\n\ud83d\udee0\ufe0f X\u00e1c \u0111\u1ecbnh c\u00e1c thu\u1ed9c t\u00ednh trong m\u00f4 h\u00ecnh d\u1eef li\u1ec7u<\/h2>\n
M\u1ed9t thu\u1ed9c t\u00ednh l\u00e0 m\u1ed9t thu\u1ed9c t\u00ednh ho\u1eb7c \u0111\u1eb7c \u0111i\u1ec3m c\u1ee7a m\u1ed9t th\u1ef1c th\u1ec3. Trong c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u1eadt l\u00fd, \u0111i\u1ec1u n\u00e0y t\u01b0\u01a1ng \u1ee9ng v\u1edbi m\u1ed9t c\u1ed9t trong b\u1ea3ng. \u1ede giai \u0111o\u1ea1n kh\u00e1i ni\u1ec7m, \u0111\u00f3 l\u00e0 h\u00ecnh tr\u00f2n ho\u1eb7c h\u00ecnh elip \u0111\u01b0\u1ee3c k\u1ebft n\u1ed1i v\u1edbi h\u00ecnh ch\u1eef nh\u1eadt th\u1ef1c th\u1ec3 trong s\u01a1 \u0111\u1ed3 ER. S\u1ef1 ph\u00e2n bi\u1ec7t gi\u1eefa th\u1ef1c th\u1ec3 v\u00e0 thu\u1ed9c t\u00ednh \u0111\u00f4i khi m\u1edd nh\u1ea1t, nh\u01b0ng quy t\u1eafc \u0111\u01a1n gi\u1ea3n l\u00e0: n\u1ebfu d\u1eef li\u1ec7u m\u00f4 t\u1ea3 th\u1ef1c th\u1ec3 v\u00e0 kh\u00f4ng th\u1ec3 t\u1ed3n t\u1ea1i \u0111\u1ed9c l\u1eadp, th\u00ec \u0111\u00f3 l\u00e0 m\u1ed9t thu\u1ed9c t\u00ednh.<\/p>\n
H\u00e3y xem x\u00e9t m\u1ed9t Kh\u00e1ch h\u00e0ng<\/strong>th\u1ef1c th\u1ec3. T\u00ean, \u0111\u1ecba ch\u1ec9 v\u00e0 ng\u00e0y sinh l\u00e0 c\u00e1c thu\u1ed9c t\u00ednh. Ch\u00fang m\u00f4 t\u1ea3 kh\u00e1ch h\u00e0ng nh\u01b0ng kh\u00f4ng t\u1ed3n t\u1ea1i nh\u01b0 c\u00e1c b\u1ea3n ghi \u0111\u1ed9c l\u1eadp gi\u1ed1ng nh\u01b0 m\u1ed9t \u0111\u01a1n h\u00e0ng hay m\u1ed9t s\u1ea3n ph\u1ea9m. Tuy nhi\u00ean, quy\u1ebft \u0111\u1ecbnh c\u00e1ch l\u01b0u tr\u1eef c\u00e1c thu\u1ed9c t\u00ednh n\u00e0y m\u1edbi l\u00e0 n\u01a1i ph\u1ee9c t\u1ea1p b\u1eaft \u0111\u1ea7u.<\/p>\nC\u00e1c lo\u1ea1i thu\u1ed9c t\u00ednh b\u1ea1n c\u1ea7n bi\u1ebft<\/h3>\n
Kh\u00f4ng ph\u1ea3i m\u1ecdi thu\u1ed9c t\u00ednh n\u00e0o c\u0169ng gi\u1ed1ng nhau. Hi\u1ec3u r\u00f5 ph\u00e2n lo\u1ea1i c\u1ee5 th\u1ec3 c\u1ee7a m\u1ed9t thu\u1ed9c t\u00ednh gi\u00fap x\u00e1c \u0111\u1ecbnh y\u00eau c\u1ea7u l\u01b0u tr\u1eef v\u00e0 gi\u1edbi h\u1ea1n c\u1ee7a n\u00f3. D\u01b0\u1edbi \u0111\u00e2y l\u00e0 b\u1ea3ng ph\u00e2n t\u00edch c\u00e1c lo\u1ea1i ph\u1ed5 bi\u1ebfn g\u1eb7p ph\u1ea3i trong qu\u00e1 tr\u00ecnh m\u00f4 h\u00ecnh h\u00f3a d\u1eef li\u1ec7u.<\/p>\n
\n\n\n| Lo\u1ea1i thu\u1ed9c t\u00ednh<\/th>\n | M\u00f4 t\u1ea3<\/th>\n | V\u00ed d\u1ee5<\/th>\n<\/tr>\n<\/thead>\n |
\n\n| Thu\u1ed9c t\u00ednh \u0111\u01a1n gi\u1ea3n<\/td>\n | Gi\u00e1 tr\u1ecb nguy\u00ean t\u1eed; kh\u00f4ng th\u1ec3 chia nh\u1ecf h\u01a1n n\u1eefa.<\/td>\n | Tu\u1ed5i, S\u1ed1 b\u1ea3o hi\u1ec3m x\u00e3 h\u1ed9i<\/td>\n<\/tr>\n |
\n| Thu\u1ed9c t\u00ednh h\u1ee3p th\u00e0nh<\/td>\n | Chia th\u00e0nh c\u00e1c ph\u1ea7n con.<\/td>\n | \u0110\u1ecba ch\u1ec9 (\u0110\u01b0\u1eddng, Th\u00e0nh ph\u1ed1, M\u00e3 b\u01b0u \u0111i\u1ec7n)<\/td>\n<\/tr>\n |
\n| Thu\u1ed9c t\u00ednh nhi\u1ec1u gi\u00e1 tr\u1ecb<\/td>\n | C\u00f3 th\u1ec3 l\u01b0u tr\u1eef nhi\u1ec1u gi\u00e1 tr\u1ecb cho m\u1ed9t th\u1ec3 hi\u1ec7n th\u1ef1c th\u1ec3 duy nh\u1ea5t.<\/td>\n | S\u1ed1 \u0111i\u1ec7n tho\u1ea1i, \u0110\u1ecba ch\u1ec9 email<\/td>\n<\/tr>\n |
\n| Thu\u1ed9c t\u00ednh suy ra<\/td>\n | T\u00ednh to\u00e1n t\u1eeb c\u00e1c thu\u1ed9c t\u00ednh kh\u00e1c.<\/td>\n | Tu\u1ed5i (t\u00ednh t\u1eeb ng\u00e0y sinh), T\u1ed5ng gi\u00e1 ti\u1ec1n<\/td>\n<\/tr>\n |
\n| Thu\u1ed9c t\u00ednh kh\u00f3a<\/td>\n | X\u00e1c \u0111\u1ecbnh duy nh\u1ea5t th\u1ef1c th\u1ec3.<\/td>\n | M\u00e3 kh\u00e1ch h\u00e0ng, S\u1ed1 \u0111\u01a1n h\u00e0ng<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n M\u1ed7i lo\u1ea1i thu\u1ed9c t\u00ednh n\u00e0y \u0111\u1ec1u y\u00eau c\u1ea7u x\u1eed l\u00fd c\u1ee5 th\u1ec3 \u1edf giai \u0111o\u1ea1n thi\u1ebft k\u1ebf logic. Vi\u1ec7c kh\u00f4ng ph\u00e2n bi\u1ec7t \u0111\u01b0\u1ee3c gi\u1eefa m\u1ed9t thu\u1ed9c t\u00ednh \u0111\u01a1n gi\u1ea3n v\u00e0 m\u1ed9t thu\u1ed9c t\u00ednh h\u1ee3p th\u00e0nh c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn c\u00e1c l\u01b0\u1ee3c \u0111\u1ed3 c\u1ee9ng nh\u1eafc, kh\u00f3 thay \u0111\u1ed5i v\u1ec1 sau. V\u00ed d\u1ee5, l\u01b0u tr\u1eef \u0111\u1ecba ch\u1ec9 \u0111\u1ea7y \u0111\u1ee7 d\u01b0\u1edbi d\u1ea1ng m\u1ed9t chu\u1ed7i duy nh\u1ea5t s\u1ebd khi\u1ebfn vi\u1ec7c l\u1ecdc theo th\u00e0nh ph\u1ed1 ho\u1eb7c m\u00e3 b\u01b0u \u0111i\u1ec7n tr\u1edf n\u00ean kh\u00f3 kh\u0103n m\u00e0 kh\u00f4ng c\u1ea7n thao t\u00e1c chu\u1ed7i ph\u1ee9c t\u1ea1p.<\/p>\n \u2696\ufe0f Chi ph\u00ed \u1ea9n \u0111\u1eb1ng sau thi\u1ebft k\u1ebf thu\u1ed9c t\u00ednh k\u00e9m hi\u1ec7u qu\u1ea3<\/h2>\nNhi\u1ec1u nh\u00f3m coi thu\u1ed9c t\u00ednh l\u00e0 chi ti\u1ebft nh\u1ecf nh\u1eb7t c\u1ea7n \u0111i\u1ec1n sau khi c\u00e1c m\u1ed1i quan h\u1ec7 \u0111\u00e3 \u0111\u01b0\u1ee3c thi\u1ebft l\u1eadp. C\u00e1ch ti\u1ebfp c\u1eadn n\u00e0y th\u01b0\u1eddng d\u1eabn \u0111\u1ebfn n\u1ee3 k\u1ef9 thu\u1eadt \u0111\u00e1ng k\u1ec3. Khi c\u00e1c thu\u1ed9c t\u00ednh \u0111\u01b0\u1ee3c \u0111\u1ecbnh ngh\u0129a k\u00e9m, h\u1ec7 qu\u1ea3 s\u1ebd lan r\u1ed9ng kh\u1eafp to\u00e0n b\u1ed9 h\u1ec7 th\u1ed1ng.<\/p>\n \n- V\u1ea5n \u0111\u1ec1 to\u00e0n v\u1eb9n d\u1eef li\u1ec7u:<\/strong> N\u1ebfu m\u1ed9t thu\u1ed9c t\u00ednh cho ph\u00e9p gi\u00e1 tr\u1ecb null m\u00e0 kh\u00f4ng c\u00f3 logic kinh doanh r\u00f5 r\u00e0ng, b\u00e1o c\u00e1o s\u1ebd tr\u1edf n\u00ean kh\u00f4ng \u0111\u00e1ng tin c\u1eady. N\u1ebfu m\u1ed9t thu\u1ed9c t\u00ednh thi\u1ebfu r\u00e0ng bu\u1ed9c (nh\u01b0 \u0111\u1ed9 d\u00e0i t\u1ed1i \u0111a ho\u1eb7c ph\u1ea1m vi h\u1ee3p l\u1ec7), c\u01a1 s\u1edf d\u1eef li\u1ec7u s\u1ebd ch\u1ea5p nh\u1eadn d\u1eef li\u1ec7u r\u00e1c.<\/li>\n
- Suy gi\u1ea3m hi\u1ec7u su\u1ea5t truy v\u1ea5n:<\/strong> Vi\u1ec7c l\u01b0u tr\u1eef d\u1eef li\u1ec7u suy di\u1ec5n m\u1ed9t c\u00e1ch d\u01b0 th\u1eeba m\u00e0 kh\u00f4ng c\u00f3 ch\u1ec9 m\u1ee5c c\u00f3 th\u1ec3 l\u00e0m ch\u1eadm thao t\u00e1c c\u1eadp nh\u1eadt. Ng\u01b0\u1ee3c l\u1ea1i, vi\u1ec7c kh\u00f4ng ch\u1ec9 m\u1ee5c h\u00f3a c\u00e1c thu\u1ed9c t\u00ednh th\u01b0\u1eddng xuy\u00ean \u0111\u01b0\u1ee3c truy v\u1ea5n c\u00f3 th\u1ec3 khi\u1ebfn thao t\u00e1c t\u00ecm ki\u1ebfm tr\u1edf n\u00ean ch\u1eadm ch\u1ea1p.<\/li>\n
- Vi ph\u1ea1m chu\u1ea9n h\u00f3a:<\/strong> Vi\u1ec7c chia t\u00e1ch ho\u1eb7c g\u1ed9p c\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng \u0111\u00fang th\u01b0\u1eddng d\u1eabn \u0111\u1ebfn c\u00e1c b\u1ea5t th\u01b0\u1eddng trong qu\u00e1 tr\u00ecnh ch\u00e8n, x\u00f3a ho\u1eb7c c\u1eadp nh\u1eadt b\u1ea3n ghi.<\/li>\n
- Ch\u1ed7 ngh\u1ebdn kh\u1ea3 n\u0103ng m\u1edf r\u1ed9ng:<\/strong> C\u00e1c thu\u1ed9c t\u00ednh ph\u00e1t tri\u1ec3n kh\u00f4ng gi\u1edbi h\u1ea1n (v\u00ed d\u1ee5 nh\u01b0 l\u01b0u danh s\u00e1ch th\u1ebb trong m\u1ed9t tr\u01b0\u1eddng v\u0103n b\u1ea3n duy nh\u1ea5t) ng\u0103n c\u1ea3n c\u00e1c chi\u1ebfn l\u01b0\u1ee3c ph\u00e2n v\u00f9ng v\u00e0 chia nh\u1ecf hi\u1ec7u qu\u1ea3.<\/li>\n<\/ul>\n
\u0110i\u1ec1u n\u00e0y kh\u00f4ng ch\u1ec9 \u0111\u01a1n thu\u1ea7n l\u00e0 c\u00f3 c\u00e1c c\u1ed9t \u0111\u00fang, m\u00e0 c\u00f2n l\u00e0 c\u00f3 c\u00e1c r\u00e0ng bu\u1ed9c v\u00e0 ki\u1ec3u d\u1eef li\u1ec7u ph\u00f9 h\u1ee3p. M\u1ed9tvarchar<\/code>tr\u01b0\u1eddng d\u00f9ng \u0111\u1ec3 l\u01b0u s\u1ed1 \u0111i\u1ec7n tho\u1ea1i s\u1ebd k\u00e9m hi\u1ec7u qu\u1ea3 v\u00e0 k\u00e9m ch\u00ednh x\u00e1c h\u01a1n so v\u1edbi ki\u1ec3u d\u1eef li\u1ec7u nguy\u00ean th\u1ee7y c\u1ee5 th\u1ec3 ho\u1eb7c ki\u1ec3u chu\u1ed7i \u0111\u1ecbnh d\u1ea1ng, v\u1ed1n ki\u1ec3m tra \u0111\u1ea7u v\u00e0o.<\/p>\n\ud83d\udd0d Kh\u00e1m ph\u00e1 s\u00e2u: M\u1eabu thi\u1ebft k\u1ebf thu\u1ed9c t\u00ednh<\/h2>\n\u0110\u1ec3 x\u00e2y d\u1ef1ng c\u00e1c h\u1ec7 th\u1ed1ng v\u1eefng ch\u1eafc, c\u00e1c nh\u00e0 thi\u1ebft k\u1ebf n\u00ean \u00e1p d\u1ee5ng c\u00e1c m\u1eabu c\u1ee5 th\u1ec3 khi \u0111\u1ecbnh ngh\u0129a thu\u1ed9c t\u00ednh. Nh\u1eefng m\u1eabu n\u00e0y \u0111\u1ea3m b\u1ea3o t\u00ednh nh\u1ea5t qu\u00e1n v\u00e0 r\u00f5 r\u00e0ng trong to\u00e0n b\u1ed9 m\u00f4 h\u00ecnh d\u1eef li\u1ec7u.<\/p>\n 1. T\u00ednh nguy\u00ean t\u1eed v\u00e0 d\u1ea1ng chu\u1ea9n th\u1ee9 nh\u1ea5t<\/h3>\nQuy t\u1eafc \u0111\u1ea7u ti\u00ean trong thi\u1ebft k\u1ebf thu\u1ed9c t\u00ednh l\u00e0 t\u00ednh nguy\u00ean t\u1eed. M\u1ed7i thu\u1ed9c t\u00ednh ph\u1ea3i ch\u1ee9a m\u1ed9t gi\u00e1 tr\u1ecb duy nh\u1ea5t, kh\u00f4ng th\u1ec3 chia nh\u1ecf. Tr\u00e1nh l\u01b0u tr\u1eef nhi\u1ec1u gi\u00e1 tr\u1ecb trong m\u1ed9t \u00f4.<\/p>\n \n- Th\u00f3i quen x\u1ea5u:<\/strong>M\u1ed9t
k\u1ef9 n\u0103ng<\/code>c\u1ed9t ch\u1ee9a \u201cSQL, Python, Java\u201d.<\/li>\n- Th\u00f3i quen t\u1ed1t:<\/strong>M\u1ed9t b\u1ea3ng li\u00ean k\u1ebft ri\u00eang bi\u1ec7t k\u1ebft n\u1ed1iNh\u00e2n vi\u00ean<\/strong>v\u00e0K\u1ef9 n\u0103ng<\/strong>.<\/li>\n<\/ul>\n
Vi ph\u1ea1m t\u00ednh nguy\u00ean t\u1eed l\u00e0m ph\u1ee9c t\u1ea1p h\u00f3a truy v\u1ea5n. B\u1ea1n kh\u00f4ng th\u1ec3 d\u1ec5 d\u00e0ng \u0111\u1ebfm xem c\u00f3 bao nhi\u00eau nh\u00e2n vi\u00ean bi\u1ebft \u201cPython\u201d n\u1ebfu kh\u00f4ng ph\u00e2n t\u00edch chu\u1ed7i. Gi\u1eef cho c\u00e1c thu\u1ed9c t\u00ednh \u1edf tr\u1ea1ng th\u00e1i nguy\u00ean t\u1eed s\u1ebd \u0111\u01a1n gi\u1ea3n h\u00f3a logic c\u1ea7n thi\u1ebft cho vi\u1ec7c truy xu\u1ea5t v\u00e0 t\u1ed5ng h\u1ee3p d\u1eef li\u1ec7u.<\/p>\n 2. Quy \u01b0\u1edbc \u0111\u1eb7t t\u00ean v\u00e0 s\u1ef1 r\u00f5 r\u00e0ng<\/h3>\nT\u00ean thu\u1ed9c t\u00ednh ph\u1ea3i t\u1ef1 gi\u1ea3i th\u00edch \u0111\u01b0\u1ee3c. S\u1ef1 m\u01a1 h\u1ed3 l\u00e0 k\u1ebb th\u00f9 c\u1ee7a kh\u1ea3 n\u0103ng b\u1ea3o tr\u00ec. Tr\u00e1nh d\u00f9ng c\u00e1c vi\u1ebft t\u1eaft c\u00f3 th\u1ec3 kh\u00f4ng r\u00f5 r\u00e0ng v\u1edbi c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n t\u01b0\u01a1ng lai. S\u1eed d\u1ee5ng danh t\u1eeb s\u1ed1 \u00edt cho c\u00e1c thu\u1ed9c t\u00ednh \u0111\u1ec3 ph\u1ea3n \u00e1nh r\u1eb1ng ch\u00fang m\u00f4 t\u1ea3 m\u1ed9t thu\u1ed9c t\u00ednh duy nh\u1ea5t c\u1ee7a th\u1ef1c th\u1ec3.<\/p>\n \n- M\u1eadp m\u1edd:<\/strong>
ng\u00e0y<\/code> ho\u1eb7c gi\u00e1 tr\u1ecb<\/code>.<\/li>\n- R\u00f5 r\u00e0ng:<\/strong>
ng\u00e0y_sinh<\/code> ho\u1eb7c gi\u00e1_tr\u1ecb_giao_d\u1ecbch<\/code>.<\/li>\n<\/ul>\nT\u00ednh nh\u1ea5t qu\u00e1n trong \u0111\u1eb7t t\u00ean c\u0169ng gi\u00fap c\u00e1c c\u00f4ng c\u1ee5 t\u1ef1 \u0111\u1ed9ng t\u1ea1o t\u00e0i li\u1ec7u v\u00e0 m\u00e3 ngu\u1ed3n. N\u1ebfu m\u00f4 h\u00ecnh s\u1eed d\u1ee5ng t\u1ea1o_l\u00fac<\/code> \u1edf m\u1ecdi n\u01a1i, c\u00e1c truy v\u1ea5n SQL \u0111\u01b0\u1ee3c sinh ra s\u1ebd tu\u00e2n theo m\u1eabu \u0111\u00f3, gi\u1ea3m t\u1ea3i nh\u1eadn th\u1ee9c cho \u0111\u1ed9i ng\u0169 k\u1ef9 s\u01b0.<\/p>\n3. X\u1eed l\u00fd t\u00ednh kh\u1ea3 d\u1ee5ng c\u1ee7a gi\u00e1 tr\u1ecb r\u1ed7ng<\/h3>\nM\u1ecdi thu\u1ed9c t\u00ednh \u0111\u1ec1u ph\u1ea3i c\u00f3 quy t\u1eafc x\u00e1c \u0111\u1ecbnh v\u1ec1 gi\u00e1 tr\u1ecb r\u1ed7ng. Trong nhi\u1ec1u h\u1ec7 th\u1ed1ng, NULL<\/code> \u0111\u01b0\u1ee3c x\u1eed l\u00fd kh\u00e1c bi\u1ec7t so v\u1edbi chu\u1ed7i r\u1ed7ng ho\u1eb7c s\u1ed1 0. Vi\u1ec7c quy\u1ebft \u0111\u1ecbnh m\u1ed9t thu\u1ed9c t\u00ednh c\u00f3 th\u1ec3 l\u00e0 r\u1ed7ng hay kh\u00f4ng n\u00ean d\u1ef1a tr\u00ean logic kinh doanh.<\/p>\n\n- Thu\u1ed9c t\u00ednh b\u1eaft bu\u1ed9c:<\/strong> N\u1ebfu m\u1ed9t Kh\u00e1ch_h\u00e0ng<\/strong> kh\u00f4ng th\u1ec3 t\u1ed3n t\u1ea1i m\u00e0 kh\u00f4ng c\u00f3 \u0111\u1ecba ch\u1ec9 email, thu\u1ed9c t\u00ednh \u0111\u00f3 n\u00ean l\u00e0
KH\u00d4NG R\u1ed6NG<\/code>.<\/li>\n- Thu\u1ed9c t\u00ednh t\u00f9y ch\u1ecdn:<\/strong> N\u1ebfu m\u1ed9t S\u1ea3n_ph\u1ea9m<\/strong> c\u00f3 th\u1ec3 kh\u00f4ng c\u00f3 t\u00ean \u0111\u1ec7m, thu\u1ed9c t\u00ednh \u0111\u00f3 n\u00ean cho ph\u00e9p
NULL<\/code>.<\/li>\n<\/ul>\nD\u00f9ng qu\u00e1 m\u1ee9c NULL<\/code> c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn l\u1ed7i logic ba gi\u00e1 tr\u1ecb trong c\u00e1c truy v\u1ea5n SQL (n\u01a1i m\u00e0NULL = NULL<\/code> l\u00e0 sai). X\u1eed l\u00fd r\u00f5 r\u00e0ng c\u00e1c gi\u00e1 tr\u1ecb NULL ngay t\u1eeb giai \u0111o\u1ea1n thi\u1ebft k\u1ebf s\u1ebd ng\u0103n ch\u1eb7n nh\u1eefng b\u1eaby logic n\u00e0y.<\/p>\n\ud83e\udde9 Thu\u1ed9c t\u00ednh so v\u1edbi M\u1ed1i quan h\u1ec7: T\u00ecm ki\u1ebfm s\u1ef1 c\u00e2n b\u1eb1ng<\/h2>\nTh\u01b0\u1eddng xuy\u00ean x\u1ea3y ra tranh lu\u1eadn v\u1ec1 vi\u1ec7c khi n\u00e0o n\u00ean d\u1eebng vi\u1ec7c th\u00eam thu\u1ed9c t\u00ednh v\u00e0 b\u1eaft \u0111\u1ea7u t\u1ea1o ra c\u00e1c th\u1ef1c th\u1ec3 m\u1edbi. \u0110\u00e2y l\u00e0 v\u1ea5n \u0111\u1ec1 kinh \u0111i\u1ec3n ‘Thu\u1ed9c t\u00ednh so v\u1edbi Th\u1ef1c th\u1ec3’. Quy\u1ebft \u0111\u1ecbnh ph\u1ee5 thu\u1ed9c v\u00e0o c\u1ea5p \u0111\u1ed9 quan h\u1ec7.<\/p>\n N\u1ebfu m\u1ed9t thu\u1ed9c t\u00ednh c\u00f3 th\u1ec3 t\u1ed3n t\u1ea1i \u0111\u1ed9c l\u1eadp ho\u1eb7c c\u00f3 t\u1eadp h\u1ee3p thu\u1ed9c t\u00ednh ri\u00eang, th\u00ec n\u00f3 c\u00f3 kh\u1ea3 n\u0103ng cao n\u00ean l\u00e0 m\u1ed9t th\u1ef1c th\u1ec3. N\u1ebfu n\u00f3 thu\u1ea7n t\u00fay mang t\u00ednh m\u00f4 t\u1ea3 v\u00e0 ph\u1ee5 thu\u1ed9c v\u00e0o th\u1ef1c th\u1ec3 cha, th\u00ec n\u00f3 v\u1eabn l\u00e0 m\u1ed9t thu\u1ed9c t\u00ednh.<\/p>\n \n- T\u00ecnh hu\u1ed1ng A:<\/strong> M\u1ed9t Xe h\u01a1i<\/strong> c\u00f3 m\u1ed9t
m\u00e0u s\u1eafc<\/code>thu\u1ed9c t\u00ednh. \u0110\u00e2y l\u00e0 m\u00f4 t\u1ea3. N\u00f3 kh\u00f4ng c\u00f3 cu\u1ed9c s\u1ed1ng ri\u00eang bi\u1ec7t.<\/li>\n- T\u00ecnh hu\u1ed1ng B:<\/strong> M\u1ed9t Xe h\u01a1i<\/strong> c\u00f3 m\u1ed9t
ch\u1ee7 s\u1edf h\u1eefu<\/code>. Ch\u1ee7 s\u1edf h\u1eefu l\u00e0 m\u1ed9t ng\u01b0\u1eddi c\u00f3 c\u00e1c thu\u1ed9c t\u00ednh ri\u00eang (t\u00ean, \u0111\u1ecba ch\u1ec9). \u0110\u00e2y l\u00e0 m\u1ed1i quan h\u1ec7 v\u1edbi m\u1ed9t th\u1ef1c th\u1ec3, ch\u1ee9 kh\u00f4ng ph\u1ea3i l\u00e0 m\u1ed9t thu\u1ed9c t\u00ednh.<\/li>\n- T\u00ecnh hu\u1ed1ng C:<\/strong> M\u1ed9t Kh\u00f3a h\u1ecdc<\/strong> c\u00f3
ch\u1ee7 \u0111\u1ec1<\/code>. N\u1ebfu c\u00e1c ch\u1ee7 \u0111\u1ec1 l\u00e0 ti\u00eau chu\u1ea9n (To\u00e1n h\u1ecdc, Khoa h\u1ecdc), ch\u00fang c\u00f3 th\u1ec3 l\u00e0 thu\u1ed9c t\u00ednh. N\u1ebfu c\u00e1c ch\u1ee7 \u0111\u1ec1 ph\u1ee9c t\u1ea1p (c\u00f3 m\u00f4 t\u1ea3, m\u1ee9c \u0111\u1ed9 kh\u00f3), th\u00ec ch\u00fang n\u00ean l\u00e0 th\u1ef1c th\u1ec3.<\/li>\n<\/ul>\nVi\u1ec7c sai l\u1ec7ch s\u1ef1 c\u00e2n b\u1eb1ng n\u00e0y d\u1eabn \u0111\u1ebfn b\u1ea3ng d\u1eef li\u1ec7u qu\u00e1 phi chu\u1ea9n h\u00f3a ho\u1eb7c m\u00f4 h\u00ecnh b\u1ecb chia nh\u1ecf m\u1ed9t c\u00e1ch kh\u00f4ng c\u1ea7n thi\u1ebft. M\u1ee5c ti\u00eau l\u00e0 thu th\u1eadp \u0111\u1ea7y \u0111\u1ee7 chi ti\u1ebft c\u1ea7n thi\u1ebft m\u00e0 kh\u00f4ng t\u1ea1o ra s\u1ef1 ph\u1ee9c t\u1ea1p m\u00e0 logic kinh doanh kh\u00f4ng c\u1ea7n \u0111\u1ebfn.<\/p>\n \ud83d\udcc9 T\u00e1c \u0111\u1ed9ng \u0111\u1ebfn Chu\u1ea9n h\u00f3a<\/h2>\nChu\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. C\u00e1c thu\u1ed9c t\u00ednh l\u00e0 \u0111\u01a1n v\u1ecb ch\u00ednh \u0111\u01b0\u1ee3c di chuy\u1ec3n trong qu\u00e1 tr\u00ecnh n\u00e0y. Hi\u1ec3u r\u00f5 c\u00e1ch c\u00e1c thu\u1ed9c t\u00ednh ho\u1ea1t \u0111\u1ed9ng l\u00e0 \u0111i\u1ec1u c\u1ea7n thi\u1ebft \u0111\u1ec3 \u0111\u1ea1t \u0111\u01b0\u1ee3c d\u1ea1ng chu\u1ea9n th\u1ee9 ba (3NF).<\/p>\n C\u00e1c ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u<\/h3>\nM\u1ed9t ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u x\u1ea3y ra khi m\u1ed9t thu\u1ed9c t\u00ednh kh\u00f4ng kh\u00f3a ph\u1ee5 thu\u1ed9c v\u00e0o m\u1ed9t thu\u1ed9c t\u00ednh kh\u00f4ng kh\u00f3a kh\u00e1c. \u0110\u00e2y l\u00e0 m\u1ed9t l\u1ed7i ph\u1ed5 bi\u1ebfn trong thi\u1ebft k\u1ebf thu\u1ed9c t\u00ednh.<\/p>\n H\u00e3y t\u01b0\u1edfng t\u01b0\u1ee3ng m\u1ed9t B\u1ea3ng Order<\/strong> b\u1ea3ng ch\u1ee9a order_id<\/code>, customer_id<\/code>, customer_name<\/code>, v\u00e0 customer_address<\/code>.<\/p>\n\ncustomer_name<\/code> ph\u1ee5 thu\u1ed9c v\u00e0o customer_id<\/code>.<\/li>\ncustomer_address<\/code> ph\u1ee5 thu\u1ed9c v\u00e0o customer_id<\/code>.<\/li>\ncustomer_name<\/code> kh\u00f4ng ph\u1ee5 thu\u1ed9c v\u00e0o order_id<\/code>.<\/li>\n<\/ul>\n\u1ede \u0111\u00e2y, customer_address<\/code> l\u00e0 ph\u1ee5 thu\u1ed9c chuy\u1ec3n ti\u1ebfp v\u00e0o order_id<\/code> th\u00f4ng qua customer_id<\/code>. \u0110\u1ec3 chu\u1ea9n h\u00f3a \u0111i\u1ec1u n\u00e0y, b\u1ea1n ph\u1ea3i di chuy\u1ec3n c\u00e1c thu\u1ed9c t\u00ednh kh\u00e1ch h\u00e0ng sang m\u1ed9t b\u1ea3ng ri\u00eang bi\u1ec7t Kh\u00e1ch h\u00e0ng<\/strong> b\u1ea3ng. \u0110i\u1ec1u n\u00e0y gi\u1ea3m dung l\u01b0\u1ee3ng l\u01b0u tr\u1eef v\u00e0 \u0111\u1ea3m b\u1ea3o r\u1eb1ng n\u1ebfu kh\u00e1ch h\u00e0ng di chuy\u1ec3n, b\u1ea1n ch\u1ec9 c\u1ea7n c\u1eadp nh\u1eadt m\u1ed9t b\u1ea3n ghi.<\/p>\nC\u00e1c ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng<\/h3>\nM\u1ecdi thu\u1ed9c t\u00ednh ph\u1ea3i c\u00f3 m\u1ed1i ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng r\u00f5 r\u00e0ng v\u00e0o kh\u00f3a ch\u00ednh. N\u1ebfu b\u1ea1n kh\u00f4ng th\u1ec3 x\u00e1c \u0111\u1ecbnh \u0111\u01b0\u1ee3c kh\u00f3a n\u00e0o x\u00e1c \u0111\u1ecbnh gi\u00e1 tr\u1ecb c\u1ee7a m\u1ed9t thu\u1ed9c t\u00ednh, th\u00ec thu\u1ed9c t\u00ednh \u0111\u00f3 kh\u00f4ng thu\u1ed9c v\u1ec1 b\u1ea3ng \u0111\u00f3. Ki\u1ec3m tra n\u00e0y r\u1ea5t quan tr\u1ecdng \u0111\u1ed1i v\u1edbi t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u.<\/p>\n Quy t\u1eafc:<\/strong> M\u1ecdi thu\u1ed9c t\u00ednh kh\u00f4ng ph\u1ea3i kh\u00f3a ph\u1ea3i cung c\u1ea5p m\u1ed9t s\u1ef1 th\u1eadt v\u1ec1 kh\u00f3a, to\u00e0n b\u1ed9 kh\u00f3a, v\u00e0 ch\u1ec9 v\u1ec1 kh\u00f3a \u0111\u00f3 m\u00e0 th\u00f4i.<\/p>\n\ud83d\udeab Nh\u1eefng sai l\u1ea7m ph\u1ed5 bi\u1ebfn c\u1ea7n tr\u00e1nh<\/h2>\nNgay c\u1ea3 nh\u1eefng nh\u00e0 thi\u1ebft k\u1ebf c\u00f3 kinh nghi\u1ec7m c\u0169ng c\u00f3 th\u1ec3 m\u1eafc b\u1eaby khi x\u00e1c \u0111\u1ecbnh c\u00e1c thu\u1ed9c t\u00ednh. D\u01b0\u1edbi \u0111\u00e2y l\u00e0 nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn nh\u1ea5t v\u00e0 c\u00e1ch ph\u00f2ng tr\u00e1nh ch\u00fang.<\/p>\n 1. L\u01b0u tr\u1eef d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c suy ra<\/h3>\nR\u1ea5t h\u1ea5p d\u1eabn khi l\u01b0u tr\u1eef c\u00e1c gi\u00e1 tr\u1ecb \u0111\u00e3 t\u00ednh to\u00e1n \u0111\u1ec3 ti\u1ebft ki\u1ec7m th\u1eddi gian t\u00ednh to\u00e1n trong c\u00e1c truy v\u1ea5n. V\u00ed d\u1ee5, l\u01b0u tr\u1eef total_price<\/code> trong b\u1ea3ng \u0111\u01a1n h\u00e0ng thay v\u00ec t\u00ednh to\u00e1n t\u1eeb line_items<\/code>.<\/p>\n\n- R\u1ee7i ro:<\/strong> Kh\u00f4ng nh\u1ea5t qu\u00e1n d\u1eef li\u1ec7u. N\u1ebfu gi\u00e1 m\u1eb7t h\u00e0ng thay \u0111\u1ed5i, t\u1ed5ng gi\u00e1 tr\u1ecb \u0111\u01a1n h\u00e0ng l\u1ecbch s\u1eed s\u1ebd tr\u1edf n\u00ean sai l\u1ec7ch tr\u1eeb khi b\u1ea1n c\u0169ng c\u1eadp nh\u1eadt tr\u01b0\u1eddng t\u1ed5ng gi\u00e1 tr\u1ecb.<\/li>\n
- Gi\u1ea3i ph\u00e1p:<\/strong> Ch\u1ec9 l\u01b0u tr\u1eef d\u1eef li\u1ec7u g\u1ed1c. T\u00ednh to\u00e1n c\u00e1c gi\u00e1 tr\u1ecb \u0111\u01b0\u1ee3c suy ra v\u00e0o th\u1eddi \u0111i\u1ec3m truy v\u1ea5n ho\u1eb7c \u1edf l\u1edbp \u1ee9ng d\u1ee5ng.<\/li>\n<\/ul>\n
2. B\u1ecf qua ki\u1ec3u d\u1eef li\u1ec7u<\/h3>\nS\u1eed d\u1ee5ng ki\u1ec3u chu\u1ed7i chung cho m\u1ecdi th\u1ee9 l\u00e0 c\u00e1ch nhanh \u0111\u1ec3 ti\u1ebft ki\u1ec7m th\u1eddi gian, nh\u01b0ng s\u1ebd t\u1ea1o ra v\u1ea5n \u0111\u1ec1 sau n\u00e0y. Ng\u00e0y th\u00e1ng \u0111\u01b0\u1ee3c l\u01b0u d\u01b0\u1edbi d\u1ea1ng chu\u1ed7i kh\u00f4ng th\u1ec3 s\u1eafp x\u1ebfp ho\u1eb7c l\u1ecdc hi\u1ec7u qu\u1ea3. S\u1ed1 \u0111\u01b0\u1ee3c l\u01b0u d\u01b0\u1edbi d\u1ea1ng chu\u1ed7i s\u1ebd ng\u0103n c\u1ea3n c\u00e1c thao t\u00e1c to\u00e1n h\u1ecdc.<\/p>\n \n- Th\u1ef1c h\u00e0nh t\u1ed1t nh\u1ea5t:<\/strong> Ch\u1ecdn ki\u1ec3u d\u1eef li\u1ec7u c\u1ee5 th\u1ec3 ph\u00f9 h\u1ee3p v\u1edbi l\u0129nh v\u1ef1c. S\u1eed d\u1ee5ng
DATE<\/code>, INT<\/code>, DECIMAL<\/code>, ho\u1eb7c BLOB<\/code> khi ph\u00f9 h\u1ee3p.<\/li>\n<\/ul>\n3. B\u1ecf qua b\u1ed9 k\u00fd t\u1ef1<\/h3>\nC\u00e1c thu\u1ed9c t\u00ednh v\u0103n b\u1ea3n y\u00eau c\u1ea7u m\u1ed9t b\u1ed9 k\u00fd t\u1ef1 \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh. N\u1ebfu b\u1ea1n gi\u1ea3 \u0111\u1ecbnh ASCII nh\u01b0ng nh\u1eadn \u0111\u1ea7u v\u00e0o UTF-8, b\u1ea1n s\u1ebd m\u1ea5t c\u00e1c k\u00fd t\u1ef1 \u0111\u1eb7c bi\u1ec7t. \u0110i\u1ec1u n\u00e0y r\u1ea5t quan tr\u1ecdng \u0111\u1ed1i v\u1edbi c\u00e1c \u1ee9ng d\u1ee5ng to\u00e0n c\u1ea7u.<\/p>\n \n- Ki\u1ec3m tra:<\/strong> \u0110\u1ea3m b\u1ea3o c\u01a1 s\u1edf d\u1eef li\u1ec7u h\u1ed7 tr\u1ee3 s\u1eafp x\u1ebfp v\u00e0 m\u00e3 h\u00f3a k\u00fd t\u1ef1 c\u1ea7n thi\u1ebft cho \u0111\u1ed1i t\u01b0\u1ee3ng ng\u01b0\u1eddi d\u00f9ng m\u1ee5c ti\u00eau c\u1ee7a b\u1ea1n.<\/li>\n<\/ul>\n
\ud83d\ude80 T\u00e1c \u0111\u1ed9ng hi\u1ec7u su\u1ea5t c\u1ee7a c\u00e1c thu\u1ed9c t\u00ednh<\/h2>\nC\u00e1c thu\u1ed9c t\u00ednh \u1ea3nh h\u01b0\u1edfng tr\u1ef1c ti\u1ebfp \u0111\u1ebfn c\u00e1ch \u0111\u1ed9ng c\u01a1 c\u01a1 s\u1edf d\u1eef li\u1ec7u truy xu\u1ea5t v\u00e0 l\u01b0u tr\u1eef d\u1eef li\u1ec7u. C\u00e1ch tri\u1ec3n khai v\u1eadt l\u00fd c\u1ee7a m\u1ed9t thu\u1ed9c t\u00ednh \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn c\u00e1c ch\u1ec9 s\u1ed1 hi\u1ec7u su\u1ea5t.<\/p>\n Chi\u1ebfn l\u01b0\u1ee3c ch\u1ec9 m\u1ee5c<\/h3>\nKh\u00f4ng ph\u1ea3i m\u1ecdi thu\u1ed9c t\u00ednh n\u00e0o c\u0169ng n\u00ean \u0111\u01b0\u1ee3c ch\u1ec9 m\u1ee5c. Ch\u1ec9 m\u1ee5c l\u00e0m t\u0103ng chi ph\u00ed cho c\u00e1c thao t\u00e1c ghi (INSERT, UPDATE, DELETE) nh\u01b0ng l\u1ea1i l\u00e0m t\u0103ng t\u1ed1c \u0111\u1ed9 cho c\u00e1c thao t\u00e1c \u0111\u1ecdc (SELECT).<\/p>\n \n- \u0110\u1ed9 \u0111a d\u1ea1ng cao:<\/strong>C\u00e1c thu\u1ed9c t\u00ednh c\u00f3 nhi\u1ec1u gi\u00e1 tr\u1ecb duy nh\u1ea5t (nh\u01b0 Email) l\u00e0 \u1ee9ng c\u1eed vi\u00ean t\u1ed1t cho ch\u1ec9 m\u1ee5c.<\/li>\n
- \u0110\u1ed9 \u0111a d\u1ea1ng th\u1ea5p:<\/strong>C\u00e1c thu\u1ed9c t\u00ednh c\u00f3 \u00edt gi\u00e1 tr\u1ecb duy nh\u1ea5t (nh\u01b0 Gi\u1edbi t\u00ednh ho\u1eb7c Tr\u1ea1ng th\u00e1i) th\u01b0\u1eddng l\u00e0 \u1ee9ng c\u1eed vi\u00ean k\u00e9m cho ch\u1ec9 m\u1ee5c tr\u1eeb khi \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng trong c\u00e1c t\u1ed5 h\u1ee3p l\u1ecdc c\u1ee5 th\u1ec3.<\/li>\n<\/ul>\n
Hi\u1ec7u qu\u1ea3 l\u01b0u tr\u1eef<\/h3>\nC\u00e1c thu\u1ed9c t\u00ednh c\u00f3 \u0111\u1ed9 d\u00e0i bi\u1ebfn c\u00f3 th\u1ec3 ti\u1ebft ki\u1ec7m kh\u00f4ng gian so v\u1edbi c\u00e1c thu\u1ed9c t\u00ednh c\u00f3 \u0111\u1ed9 d\u00e0i c\u1ed1 \u0111\u1ecbnh, nh\u01b0ng c\u00f3 th\u1ec3 g\u00e2y ra ph\u00e2n m\u1ea3nh. Hi\u1ec3u r\u00f5 b\u1ed9 \u0111\u1ed9ng c\u01a1 l\u01b0u tr\u1eef l\u00e0 \u0111i\u1ec1u quan tr\u1ecdng.<\/p>\n \n- \u0110\u1ed9 d\u00e0i c\u1ed1 \u0111\u1ecbnh:<\/strong>Truy xu\u1ea5t nhanh h\u01a1n, nh\u01b0ng l\u00e3ng ph\u00ed kh\u00f4ng gian n\u1ebfu d\u1eef li\u1ec7u ng\u1eafn.<\/li>\n
- \u0110\u1ed9 d\u00e0i bi\u1ebfn:<\/strong>Ti\u1ebft ki\u1ec7m kh\u00f4ng gian, truy xu\u1ea5t ch\u1eadm h\u01a1n m\u1ed9t ch\u00fat do chi ph\u00ed metadata.<\/li>\n<\/ul>\n
\u2705 Danh s\u00e1ch ki\u1ec3m tra thi\u1ebft k\u1ebf thu\u1ed9c t\u00ednh<\/h2>\nTr\u01b0\u1edbc khi ho\u00e0n t\u1ea5t s\u01a1 \u0111\u1ed3 ER c\u1ee7a b\u1ea1n, h\u00e3y \u0111i qua danh s\u00e1ch ki\u1ec3m tra n\u00e0y \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o c\u00e1c thu\u1ed9c t\u00ednh c\u1ee7a b\u1ea1n \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf v\u1eefng ch\u1eafc.<\/p>\n \n- \u2611\ufe0f M\u1ed7i thu\u1ed9c t\u00ednh c\u00f3 ph\u1ea3i l\u00e0 nguy\u00ean t\u1eed (kh\u00f4ng c\u00f3 danh s\u00e1ch trong m\u1ed9t tr\u01b0\u1eddng duy nh\u1ea5t)?<\/li>\n
- \u2611\ufe0f M\u1ed7i thu\u1ed9c t\u00ednh c\u00f3 t\u00ean duy nh\u1ea5t v\u00e0 m\u00f4 t\u1ea3 r\u00f5 r\u00e0ng kh\u00f4ng?<\/li>\n
- \u2611\ufe0f Ki\u1ec3u d\u1eef li\u1ec7u c\u00f3 ph\u00f9 h\u1ee3p v\u1edbi gi\u00e1 tr\u1ecb mong \u0111\u1ee3i kh\u00f4ng?<\/li>\n
- \u2611\ufe0f C\u00e1c r\u00e0ng bu\u1ed9c cho ph\u00e9p null \u0111\u00e3 \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh cho t\u1ea5t c\u1ea3 c\u00e1c tr\u01b0\u1eddng ch\u01b0a?<\/li>\n
- \u2611\ufe0f C\u00e1c thu\u1ed9c t\u00ednh \u0111\u01b0\u1ee3c suy ra \u0111\u00e3 \u0111\u01b0\u1ee3c lo\u1ea1i b\u1ecf \u0111\u1ec3 thay th\u1ebf b\u1eb1ng t\u00ednh to\u00e1n?<\/li>\n
- \u2611\ufe0f C\u00f3 thu\u1ed9c t\u00ednh n\u00e0o vi ph\u1ea1m quy t\u1eafc chu\u1ea9n h\u00f3a kh\u00f4ng?<\/li>\n
- \u2611\ufe0f K\u00edch th\u01b0\u1edbc l\u01b0u tr\u1eef c\u00f3 \u0111\u01b0\u1ee3c t\u1ed1i \u01b0u h\u00f3a cho kh\u1ed1i l\u01b0\u1ee3ng d\u1eef li\u1ec7u mong \u0111\u1ee3i kh\u00f4ng?<\/li>\n
- \u2611\ufe0f C\u00e1c kh\u00f3a ngo\u1ea1i c\u00f3 \u0111\u01b0\u1ee3c li\u00ean k\u1ebft \u0111\u00fang v\u1edbi c\u00e1c thu\u1ed9c t\u00ednh cha kh\u00f4ng?<\/li>\n<\/ul>\n
Ch\u1ea5p nh\u1eadn danh s\u00e1ch n\u00e0y s\u1ebd \u0111\u1ea3m b\u1ea3o n\u1ec1n t\u1ea3ng c\u1ee7a m\u00f4 h\u00ecnh d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n \u0111\u01b0\u1ee3c v\u1eefng ch\u1eafc. N\u00f3 chuy\u1ec3n s\u1ef1 t\u1eadp trung t\u1eeb “n\u00f3 c\u00f3 ho\u1ea1t \u0111\u1ed9ng ngay b\u00e2y gi\u1edd” sang “n\u00f3 c\u00f3 ho\u1ea1t \u0111\u1ed9ng trong nhi\u1ec1u n\u0103m”.<\/p>\n \ud83d\udd17 S\u1ef1 t\u01b0\u01a1ng t\u00e1c gi\u1eefa c\u00e1c thu\u1ed9c t\u00ednh trong c\u00e1c h\u1ec7 th\u1ed1ng ph\u1ee9c t\u1ea1p<\/h2>\nTrong c\u00e1c h\u1ec7 th\u1ed1ng ph\u1ee9c t\u1ea1p, c\u00e1c thu\u1ed9c t\u00ednh th\u01b0\u1eddng tr\u1ea3i d\u00e0i qua nhi\u1ec1u ng\u1eef c\u1ea3nh kh\u00e1c nhau. H\u00e3y xem x\u00e9t m\u1ed9t nh\u1eadt k\u00fd ki\u1ec3m to\u00e1n. B\u1ea1n c\u00f3 th\u1ec3 c\u1ea7n m\u1ed9t thu\u1ed9c t\u00ednh \u0111\u1ec3 theo d\u00f5i ai \u0111\u00e3 thay \u0111\u1ed5i m\u1ed9t b\u1ea3n ghi v\u00e0 khi n\u00e0o. \u0110i\u1ec1u n\u00e0y th\u01b0\u1eddng \u0111\u01b0\u1ee3c tri\u1ec3n khai nh\u01b0 m\u1ed9t t\u1eadp h\u1ee3p c\u00e1c thu\u1ed9c t\u00ednh tr\u00ean m\u1ed7i b\u1ea3ng (t\u1ea1o_b\u1edfi<\/code>, t\u1ea1o_v\u00e0o_l\u00fac<\/code>, c\u1eadp_nh\u1eadt_b\u1edfi<\/code>, c\u1eadp_nh\u1eadt_v\u00e0o_l\u00fac<\/code>).<\/p>\nM\u1eb7c d\u00f9 \u0111i\u1ec1u n\u00e0y t\u1ea1o ra s\u1ef1 tr\u00f9ng l\u1eb7p, nh\u01b0ng \u0111\u00f3 l\u00e0 m\u1ed9t l\u1ef1a ch\u1ecdn thi\u1ebft k\u1ebf c\u00f3 ch\u1ee7 \u00fd nh\u1eb1m \u0111\u1ea3m b\u1ea3o kh\u1ea3 n\u0103ng truy xu\u1ea5t ngu\u1ed3n g\u1ed1c. Trong tr\u01b0\u1eddng h\u1ee3p n\u00e0y, c\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng ch\u1ec9 l\u00e0 c\u00e1c \u0111i\u1ec3m d\u1eef li\u1ec7u; ch\u00fang l\u00e0 d\u1eef li\u1ec7u meta c\u1ee7a h\u1ec7 th\u1ed1ng. Hi\u1ec3u r\u00f5 m\u1ee5c \u0111\u00edch c\u1ee7a t\u1eebng thu\u1ed9c t\u00ednh l\u00e0 ch\u00eca kh\u00f3a \u0111\u1ec3 qu\u1ea3n l\u00fd s\u1ef1 ph\u1ee9c t\u1ea1p n\u00e0y.<\/p>\n M\u1ed9t y\u1ebfu t\u1ed1 c\u1ea7n c\u00e2n nh\u1eafc kh\u00e1c l\u00e0 to\u00e0n c\u1ea7u h\u00f3a. C\u00e1c thu\u1ed9c t\u00ednh nh\u01b0 t\u00ean ho\u1eb7c \u0111\u1ecba ch\u1ec9 ph\u1ea3i x\u1eed l\u00fd \u0111\u01b0\u1ee3c c\u00e1c \u0111\u1ecbnh d\u1ea1ng kh\u00e1c nhau. M\u1ed9t c\u1ea5u tr\u00fac thu\u1ed9c t\u00ednh duy nh\u1ea5t c\u00f3 th\u1ec3 kh\u00f4ng \u0111\u1ee7 \u0111\u00e1p \u1ee9ng nhu c\u1ea7u c\u1ee7a m\u1ed9t c\u01a1 s\u1edf ng\u01b0\u1eddi d\u00f9ng to\u00e0n c\u1ea7u. Thi\u1ebft k\u1ebf linh ho\u1ea1t t\u1eeb \u0111\u1ea7u\u2014v\u00ed d\u1ee5 nh\u01b0 s\u1eed d\u1ee5ng c\u00e1c thu\u1ed9c t\u00ednh ri\u00eang bi\u1ec7t cho t\u00ean v\u00e0 h\u1ecd thay v\u00ec m\u1ed9t chu\u1ed7i duy nh\u1ea5t t\u00ean_\u0111\u1ea7y_\u0111\u1ee7<\/code> chu\u1ed7i\u2014c\u00f3 th\u1ec3 ti\u1ebft ki\u1ec7m \u0111\u00e1ng k\u1ec3 n\u1ed7 l\u1ef1c t\u00e1i c\u1ea5u tr\u00fac v\u1ec1 sau.<\/p>\n\ud83d\udee1\ufe0f C\u00e1c c\u00e2n nh\u1eafc v\u1ec1 b\u1ea3o m\u1eadt v\u00e0 quy\u1ec1n ri\u00eang t\u01b0<\/h2>\nC\u00e1c thu\u1ed9c t\u00ednh th\u01b0\u1eddng ch\u1ee9a th\u00f4ng tin nh\u1ea1y c\u1ea3m. Thi\u1ebft k\u1ebf b\u1ea3o m\u1eadt b\u1eaft \u0111\u1ea7u b\u1eb1ng vi\u1ec7c x\u00e1c \u0111\u1ecbnh nh\u1eefng thu\u1ed9c t\u00ednh n\u00e0o c\u1ea7n \u0111\u01b0\u1ee3c b\u1ea3o v\u1ec7.<\/p>\n \n- PII (Th\u00f4ng tin nh\u1eadn d\u1ea1ng c\u00e1 nh\u00e2n):<\/strong>T\u00ean, \u0111\u1ecba ch\u1ec9 v\u00e0 m\u00e3 \u0111\u1ecbnh danh y\u00eau c\u1ea7u m\u00e3 h\u00f3a khi l\u01b0u tr\u1eef v\u00e0 khi truy\u1ec1n t\u1ea3i.<\/li>\n
- Ki\u1ec3m so\u00e1t truy c\u1eadp:<\/strong> M\u1ed9t s\u1ed1 thu\u1ed9c t\u00ednh ch\u1ec9 n\u00ean \u0111\u01b0\u1ee3c hi\u1ec3n th\u1ecb cho c\u00e1c vai tr\u00f2 c\u1ee5 th\u1ec3. S\u01a1 \u0111\u1ed3 ER n\u00ean ghi ch\u00fa r\u00f5 c\u00e1c tr\u01b0\u1eddng n\u00e0o l\u00e0 nh\u1ea1y c\u1ea3m, ngay c\u1ea3 khi vi\u1ec7c ki\u1ec3m so\u00e1t truy c\u1eadp \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n \u1edf l\u1edbp \u1ee9ng d\u1ee5ng.<\/li>\n
- Tu\u00e2n th\u1ee7:<\/strong>C\u00e1c quy \u0111\u1ecbnh nh\u01b0 GDPR hay CCPA \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn th\u1eddi gian b\u1ea1n l\u01b0u tr\u1eef m\u1ed9t s\u1ed1 thu\u1ed9c t\u00ednh nh\u1ea5t \u0111\u1ecbnh. Thi\u1ebft k\u1ebf l\u01b0\u1ee3c \u0111\u1ed3 \u0111\u1ec3 h\u1ed7 tr\u1ee3 c\u00e1c ch\u00ednh s\u00e1ch l\u01b0u tr\u1eef d\u1eef li\u1ec7u (v\u00ed d\u1ee5 nh\u01b0
h\u1ebft_h\u1ea1n_v\u00e0o_l\u00fac<\/code> thu\u1ed9c t\u00ednh) s\u1ebd gi\u00fap tu\u00e2n th\u1ee7 t\u1ed1t h\u01a1n.<\/li>\n<\/ul>\nB\u1ecf qua c\u00e1c c\u00e2n nh\u1eafc n\u00e0y trong giai \u0111o\u1ea1n m\u00f4 h\u00ecnh h\u00f3a c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn c\u00e1c b\u1ea3n v\u00e1 b\u1ea3o m\u1eadt t\u1ed1n k\u00e9m ho\u1eb7c c\u00e1c v\u1ea5n \u0111\u1ec1 ph\u00e1p l\u00fd v\u1ec1 sau. X\u1eed l\u00fd c\u00e1c thu\u1ed9c t\u00ednh nh\u1ea1y c\u1ea3m v\u1edbi c\u00f9ng m\u1ee9c \u0111\u1ed9 nghi\u00eam ng\u1eb7t nh\u01b0 c\u00e1c thu\u1ed9c t\u00ednh c\u1ea5u tr\u00fac.<\/p>\n \ud83d\udcdd T\u00f3m t\u1eaft nh\u1eefng \u0111i\u1ec3m ch\u00ednh c\u1ea7n l\u01b0u \u00fd<\/h2>\nC\u00e1c thu\u1ed9c t\u00ednh l\u00e0 b\u1ea3n ch\u1ea5t c\u1ee7a c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n. Kh\u00f4ng c\u00f3 ch\u00fang, c\u00e1c m\u1ed1i quan h\u1ec7 ch\u1ec9 l\u00e0 nh\u1eefng \u0111\u01b0\u1eddng th\u1eb3ng tr\u1ed1ng r\u1ed7ng n\u1ed1i c\u00e1c h\u1ed9p tr\u1ed1ng. M\u1ed9t t\u1eadp h\u1ee3p thu\u1ed9c t\u00ednh \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf t\u1ed1t \u0111\u1ea3m b\u1ea3o d\u1eef li\u1ec7u ch\u00ednh x\u00e1c, hi\u1ec7u qu\u1ea3 v\u00e0 an to\u00e0n.<\/p>\n \n- T\u1eadp trung v\u00e0o t\u00ednh nguy\u00ean t\u1eed:<\/strong>Gi\u1eef d\u1eef li\u1ec7u \u1edf m\u1ee9c chi ti\u1ebft v\u00e0 kh\u00f4ng th\u1ec3 chia nh\u1ecf.<\/li>\n
- T\u00f4n tr\u1ecdng chu\u1ea9n h\u00f3a:<\/strong>Lo\u1ea1i b\u1ecf c\u00e1c ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u \u0111\u1ec3 ng\u0103n ng\u1eeba c\u00e1c b\u1ea5t th\u01b0\u1eddng.<\/li>\n
- X\u00e1c \u0111\u1ecbnh c\u00e1c r\u00e0ng bu\u1ed9c:<\/strong>S\u1eed d\u1ee5ng ki\u1ec3u d\u1eef li\u1ec7u v\u00e0 kh\u1ea3 n\u0103ng ch\u1ea5p nh\u1eadn gi\u00e1 tr\u1ecb r\u1ed7ng \u0111\u1ec3 th\u1ef1c thi c\u00e1c quy t\u1eafc kinh doanh.<\/li>\n
- Xem x\u00e9t hi\u1ec7u su\u1ea5t:<\/strong>Ch\u1ec9 m\u1ee5c m\u1ed9t c\u00e1ch kh\u00f4n ngoan v\u00e0 ch\u1ecdn lo\u1ea1i l\u01b0u tr\u1eef m\u1ed9t c\u00e1ch c\u1ea9n tr\u1ecdng.<\/li>\n
- L\u00ean k\u1ebf ho\u1ea1ch cho b\u1ea3o m\u1eadt:<\/strong>X\u00e1c \u0111\u1ecbnh d\u1eef li\u1ec7u nh\u1ea1y c\u1ea3m t\u1eeb s\u1edbm.<\/li>\n<\/ul>\n
B\u1eb1ng c\u00e1ch d\u00e0nh th\u1eddi gian cho nh\u1eefng chi ti\u1ebft tinh t\u1ebf trong thi\u1ebft k\u1ebf thu\u1ed9c t\u00ednh, b\u1ea1n s\u1ebd t\u1ea1o ra m\u1ed9t m\u00f4 h\u00ecnh d\u1eef li\u1ec7u c\u00f3 kh\u1ea3 n\u0103ng ch\u1ed1ng ch\u1ecbu t\u1ed1t tr\u01b0\u1edbc s\u1ef1 thay \u0111\u1ed5i v\u00e0 ho\u1ea1t \u0111\u1ed9ng hi\u1ec7u qu\u1ea3. S\u1ee9c m\u1ea1nh c\u1ee7a s\u01a1 \u0111\u1ed3 ER kh\u00f4ng ch\u1ec9 n\u1eb1m \u1edf c\u00e1c m\u1ed1i li\u00ean k\u1ebft, m\u00e0 c\u00f2n n\u1eb1m \u1edf \u0111\u1ed9 ch\u00ednh x\u00e1c c\u1ee7a nh\u1eefng chi ti\u1ebft m\u00e0 n\u00f3 ghi l\u1ea1i.<\/p>\n","protected":false},"excerpt":{"rendered":" Khi c\u00e1c ki\u1ebfn tr\u00fac s\u01b0 b\u1eaft \u0111\u1ea7u thi\u1ebft k\u1ebf c\u1ea5u tr\u00fac d\u1eef li\u1ec7u, s\u1ef1 ch\u00fa \u00fd th\u01b0\u1eddng d\u1ed3n v\u00e0o c\u00e1c m\u1ed1i li\u00ean k\u1ebft. Ch\u00fang ta t\u1eadp trung nhi\u1ec1u v\u00e0o c\u00e1c…<\/p>\n","protected":false},"author":1,"featured_media":68,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_yoast_wpseo_title":"S\u1ee9c m\u1ea1nh c\u1ee7a c\u00e1c thu\u1ed9c t\u00ednh trong s\u01a1 \u0111\u1ed3 ER: T\u1ea1i sao ch\u00fang quan tr\u1ecdng h\u01a1n b\u1ea1n ngh\u0129","_yoast_wpseo_metadesc":"Kh\u00e1m ph\u00e1 c\u00e1ch c\u00e1c thu\u1ed9c t\u00ednh trong s\u01a1 \u0111\u1ed3 Th\u1ef1c th\u1ec3 - Li\u00ean k\u1ebft th\u00fac \u0111\u1ea9y t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u, hi\u1ec7u su\u1ea5t v\u00e0 kh\u1ea3 n\u0103ng m\u1edf r\u1ed9ng. 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