![\"Kawaii-style](\"https:\/\/www.go-diagram.com\/wp-content\/uploads\/2026\/03\/erd-fundamentals-kawaii-infographic-beginners-guide.jpg\"\/)
<\/figure>\n<\/div>\nS\u01a1 \u0111\u1ed3 Th\u1ef1c th\u1ec3 – Quan h\u1ec7 l\u00e0 g\u00ec? \ud83e\udd14<\/h2>\n
ERD l\u00e0 m\u1ed9t bi\u1ec3u di\u1ec5n \u0111\u1ed3 h\u1ecda c\u1ee7a m\u1ed9t h\u1ec7 th\u1ed1ng th\u00f4ng tin. N\u00f3 m\u00f4 t\u1ea3 c\u00e1c th\u1ef1c th\u1ec3, thu\u1ed9c t\u00ednh v\u00e0 m\u1ed1i quan h\u1ec7 gi\u1eefa ch\u00fang. H\u00e3y h\u00ecnh dung n\u00f3 nh\u01b0 m\u1ed9t b\u1ea3n \u0111\u1ed3 cho d\u1eef li\u1ec7u. T\u01b0\u01a1ng t\u1ef1 nh\u01b0 b\u1ea3n \u0111\u1ed3 th\u00e0nh ph\u1ed1 hi\u1ec3n th\u1ecb c\u00e1c con \u0111\u01b0\u1eddng, t\u00f2a nh\u00e0 v\u00e0 c\u00f4ng vi\u00ean, ERD th\u1ec3 hi\u1ec7n c\u00e1c b\u1ea3ng, c\u1ed9t v\u00e0 c\u00e1c k\u1ebft n\u1ed1i.<\/p>\n
M\u1ee5c \u0111\u00edch ch\u00ednh c\u1ee7a ERD l\u00e0 h\u1ed7 tr\u1ee3 giao ti\u1ebfp gi\u1eefa c\u00e1c b\u00ean li\u00ean quan. C\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n, chuy\u00ean vi\u00ean ph\u00e2n t\u00edch kinh doanh v\u00e0 qu\u1ea3n l\u00fd d\u1ef1 \u00e1n s\u1eed d\u1ee5ng c\u00e1c s\u01a1 \u0111\u1ed3 n\u00e0y \u0111\u1ec3 th\u1ed1ng nh\u1ea5t v\u1ec1 y\u00eau c\u1ea7u d\u1eef li\u1ec7u tr\u01b0\u1edbc khi vi\u1ebft b\u1ea5t k\u1ef3 d\u00f2ng m\u00e3 n\u00e0o. \u0110i\u1ec1u n\u00e0y gi\u00fap gi\u1ea3m thi\u1ec3u l\u1ed7i v\u00e0 c\u00f4ng vi\u1ec7c ph\u1ea3i l\u00e0m l\u1ea1i trong su\u1ed1t v\u00f2ng \u0111\u1eddi ph\u00e1t tri\u1ec3n.<\/p>\n
L\u1ee3i \u00edch ch\u00ednh khi s\u1eed d\u1ee5ng ERD<\/h3>\n\n- \n
R\u00f5 r\u00e0ng v\u1ec1 m\u1eb7t tr\u1ef1c quan:<\/strong>C\u00e1c c\u1ea5u tr\u00fac d\u1eef li\u1ec7u ph\u1ee9c t\u1ea1p tr\u1edf n\u00ean d\u1ec5 hi\u1ec3u h\u01a1n khi \u0111\u01b0\u1ee3c v\u1ebd ra.<\/p>\n<\/li>\n- \n
Ti\u00eau chu\u1ea9n h\u00f3a:<\/strong>Cung c\u1ea5p m\u1ed9t ng\u00f4n ng\u1eef chung cho c\u00e1c \u0111\u1ed9i k\u1ef9 thu\u1eadt v\u00e0 kh\u00f4ng k\u1ef9 thu\u1eadt.<\/p>\n<\/li>\n- \n
Hi\u1ec7u qu\u1ea3:<\/strong>Ph\u00e1t hi\u1ec7n s\u1edbm c\u00e1c v\u1ea5n \u0111\u1ec1 ti\u1ec1m \u1ea9n nh\u01b0 d\u1eef li\u1ec7u tr\u00f9ng l\u1eb7p.<\/p>\n<\/li>\n- \n
T\u00e0i li\u1ec7u tham kh\u1ea3o:<\/strong>L\u00e0 t\u00e0i li\u1ec7u tham kh\u1ea3o cho vi\u1ec7c b\u1ea3o tr\u00ec v\u00e0 m\u1edf r\u1ed9ng trong t\u01b0\u01a1ng lai.<\/p>\n<\/li>\n<\/ul>\nC\u00e1c th\u00e0nh ph\u1ea7n c\u1ed1t l\u00f5i c\u1ee7a ERD \ud83d\udd27<\/h2>\n
M\u1ed7i s\u01a1 \u0111\u1ed3 bao g\u1ed3m ba kh\u1ed1i x\u00e2y d\u1ef1ng c\u01a1 b\u1ea3n. Vi\u1ec7c hi\u1ec3u r\u00f5 nh\u1eefng kh\u1ed1i n\u00e0y l\u00e0 b\u01b0\u1edbc \u0111\u1ea7u ti\u00ean \u0111\u1ec3 t\u1ea1o ra m\u1ed9t l\u01b0\u1ee3c \u0111\u1ed3 v\u1eefng ch\u1eafc.<\/p>\n
1. Th\u1ef1c th\u1ec3 \ud83c\udfe2<\/h3>\n
M\u1ed9t th\u1ef1c th\u1ec3 \u0111\u1ea1i di\u1ec7n cho m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng ho\u1eb7c kh\u00e1i ni\u1ec7m trong th\u1ebf gi\u1edbi th\u1ef1c m\u00e0 d\u1eef li\u1ec7u c\u1ea7n \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef. Trong ng\u1eef c\u1ea3nh c\u01a1 s\u1edf d\u1eef li\u1ec7u, m\u1ed9t th\u1ef1c th\u1ec3 th\u01b0\u1eddng t\u01b0\u01a1ng \u1ee9ng v\u1edbi m\u1ed9t b\u1ea3ng.<\/p>\n
\n- \n
Th\u1ef1c th\u1ec3 m\u1ea1nh:<\/strong>Ch\u00fang t\u1ed3n t\u1ea1i \u0111\u1ed9c l\u1eadp. V\u00ed d\u1ee5, b\u1ea3ng \u201cKh\u00e1ch h\u00e0ng\u201d t\u1ed3n t\u1ea1i d\u00f9 kh\u00f4ng ph\u1ee5 thu\u1ed9c v\u00e0o c\u00e1c b\u1ea3ng kh\u00e1c.<\/p>\n<\/li>\n- \n
Th\u1ef1c th\u1ec3 y\u1ebfu:<\/strong>Ch\u00fang ph\u1ee5 thu\u1ed9c v\u00e0o m\u1ed9t th\u1ef1c th\u1ec3 kh\u00e1c \u0111\u1ec3 t\u1ed3n t\u1ea1i. M\u1ed9t \u201cChi ti\u1ebft h\u00f3a \u0111\u01a1n\u201d c\u00f3 th\u1ec3 kh\u00f4ng c\u00f3 \u00fd ngh\u0129a n\u1ebfu kh\u00f4ng c\u00f3 \u201cH\u00f3a \u0111\u01a1n\u201d.<\/p>\n<\/li>\n<\/ul>\nC\u00e1c th\u1ef1c th\u1ec3 th\u01b0\u1eddng \u0111\u01b0\u1ee3c bi\u1ec3u di\u1ec5n b\u1eb1ng h\u00ecnh ch\u1eef nh\u1eadt. T\u00ean b\u00ean trong h\u00ecnh ch\u1eef nh\u1eadt l\u00e0 s\u1ed1 nhi\u1ec1u, cho th\u1ea5y b\u1ea3ng m\u00e0 n\u00f3 \u0111\u1ea1i di\u1ec7n.<\/p>\n
2. Thu\u1ed9c t\u00ednh \ud83c\udff7\ufe0f<\/h3>\n
C\u00e1c thu\u1ed9c t\u00ednh m\u00f4 t\u1ea3 c\u00e1c thu\u1ed9c t\u00ednh ho\u1eb7c \u0111\u1eb7c \u0111i\u1ec3m c\u1ee7a m\u1ed9t th\u1ef1c th\u1ec3. Ch\u00fang t\u01b0\u01a1ng \u1ee9ng v\u1edbi c\u00e1c c\u1ed9t trong m\u1ed9t b\u1ea3ng c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/p>\n
\n- \n
Kh\u00f3a ch\u00ednh:<\/strong>M\u1ed9t \u0111\u1ecbnh danh duy nh\u1ea5t cho m\u1ed7i b\u1ea3n ghi. V\u1edbi kh\u00e1ch h\u00e0ng, \u0111i\u1ec1u n\u00e0y c\u00f3 th\u1ec3 l\u00e0 \u201cM\u00e3Kh\u00e1chH\u00e0ng\u201d.<\/p>\n<\/li>\n- \n
Kh\u00f3a ngo\u1ea1i:<\/strong>M\u1ed9t tr\u01b0\u1eddng li\u00ean k\u1ebft \u0111\u1ebfn kh\u00f3a ch\u00ednh c\u1ee7a m\u1ed9t b\u1ea3ng kh\u00e1c.<\/p>\n<\/li>\n- \n
Thu\u1ed9c t\u00ednh \u0111\u01a1n gi\u1ea3n:<\/strong> M\u1ed9t gi\u00e1 tr\u1ecb kh\u00f4ng th\u1ec3 chia t\u00e1ch, v\u00ed d\u1ee5 nh\u01b0 m\u1ed9t \u201cS\u1ed1 \u0111i\u1ec7n tho\u1ea1i\u201d.<\/p>\n<\/li>\n- \n
Thu\u1ed9c t\u00ednh h\u1ee3p th\u00e0nh:<\/strong> M\u1ed9t thu\u1ed9c t\u00ednh c\u00f3 th\u1ec3 chia th\u00e0nh c\u00e1c ph\u1ea7n nh\u1ecf h\u01a1n, v\u00ed d\u1ee5 nh\u01b0 \u201c\u0110\u1ecba ch\u1ec9\u201d (\u0110\u01b0\u1eddng, Th\u00e0nh ph\u1ed1, M\u00e3 b\u01b0u ch\u00ednh).<\/p>\n<\/li>\n- \n
Thu\u1ed9c t\u00ednh nhi\u1ec1u gi\u00e1 tr\u1ecb:<\/strong> M\u1ed9t thu\u1ed9c t\u00ednh c\u00f3 th\u1ec3 ch\u1ee9a nhi\u1ec1u gi\u00e1 tr\u1ecb, v\u00ed d\u1ee5 nh\u01b0 \u201cEmailAddresses\u201d.<\/p>\n<\/li>\n- \n
Thu\u1ed9c t\u00ednh suy ra:<\/strong> M\u1ed9t gi\u00e1 tr\u1ecb \u0111\u01b0\u1ee3c t\u00ednh to\u00e1n t\u1eeb c\u00e1c thu\u1ed9c t\u00ednh kh\u00e1c, v\u00ed d\u1ee5 nh\u01b0 \u201cTu\u1ed5i\u201d \u0111\u01b0\u1ee3c suy ra t\u1eeb \u201cNg\u00e0y sinh\u201d.<\/p>\n<\/li>\n<\/ul>\n3. M\u1ed1i quan h\u1ec7 \ud83d\udd17<\/h3>\n
C\u00e1c m\u1ed1i quan h\u1ec7 x\u00e1c \u0111\u1ecbnh c\u00e1ch c\u00e1c th\u1ef1c th\u1ec3 t\u01b0\u01a1ng t\u00e1c v\u1edbi nhau. Ch\u00fang m\u00f4 t\u1ea3 c\u00e1c k\u1ebft n\u1ed1i gi\u1eefa c\u00e1c \u0111i\u1ec3m d\u1eef li\u1ec7u.<\/p>\n
\n- \n
M\u1ed1i quan h\u1ec7 li\u00ean k\u1ebft:<\/strong> Ch\u00fang k\u1ebft n\u1ed1i hai ho\u1eb7c nhi\u1ec1u th\u1ef1c th\u1ec3.<\/p>\n<\/li>\n- \n
M\u1ed1i quan h\u1ec7 x\u00e1c \u0111\u1ecbnh:<\/strong> Ch\u00fang x\u00e1c \u0111\u1ecbnh s\u1ef1 t\u1ed3n t\u1ea1i c\u1ee7a m\u1ed9t th\u1ef1c th\u1ec3 y\u1ebfu.<\/p>\n<\/li>\n<\/ul>\nTrong s\u01a1 \u0111\u1ed3, c\u00e1c m\u1ed1i quan h\u1ec7 th\u01b0\u1eddng \u0111\u01b0\u1ee3c bi\u1ec3u di\u1ec5n b\u1eb1ng h\u00ecnh thoi ho\u1eb7c c\u00e1c \u0111\u01b0\u1eddng n\u1ed1i gi\u1eefa c\u00e1c th\u1ef1c th\u1ec3. Lo\u1ea1i m\u1ed1i quan h\u1ec7 \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh b\u1edfi t\u00ednh cardinality.<\/p>\n
Cardinality v\u00e0 T\u00ednh b\u1eaft bu\u1ed9c \ud83d\udccf<\/h2>\n
Cardinality x\u00e1c \u0111\u1ecbnh s\u1ed1 l\u01b0\u1ee3ng th\u1ec3 hi\u1ec7n c\u1ee7a m\u1ed9t th\u1ef1c th\u1ec3 c\u00f3 th\u1ec3 ho\u1eb7c ph\u1ea3i li\u00ean k\u1ebft v\u1edbi m\u1ed7i th\u1ec3 hi\u1ec7n c\u1ee7a th\u1ef1c th\u1ec3 kh\u00e1c. T\u00ednh b\u1eaft bu\u1ed9c x\u00e1c \u0111\u1ecbnh m\u1ed1i quan h\u1ec7 l\u00e0 b\u1eaft bu\u1ed9c hay t\u00f9y ch\u1ecdn.<\/p>\n
C\u00e1c lo\u1ea1i Cardinality<\/h3>\n
\n\n \n\n\nCardinality<\/p>\n<\/th>\n
\nM\u00f4 t\u1ea3<\/p>\n<\/th>\n
\nV\u00ed d\u1ee5 t\u00ecnh hu\u1ed1ng<\/p>\n<\/th>\n<\/tr>\n
\n\nM\u1ed9t-\u0111\u1ed1i-m\u1ed9t (1:1)<\/p>\n<\/td>\n
\nM\u1ed9t th\u1ec3 hi\u1ec7n li\u00ean k\u1ebft v\u1edbi \u0111\u00fang m\u1ed9t th\u1ec3 hi\u1ec7n kh\u00e1c.<\/p>\n<\/td>\n
\nM\u1ed9t Ng\u01b0\u1eddi c\u00f3 m\u1ed9t H\u1ed9 chi\u1ebfu.<\/p>\n<\/td>\n<\/tr>\n
\n\nM\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u (1:N)<\/p>\n<\/td>\n
\nM\u1ed9t th\u1ec3 hi\u1ec7n li\u00ean k\u1ebft v\u1edbi nhi\u1ec1u th\u1ec3 hi\u1ec7n c\u1ee7a th\u1ef1c th\u1ec3 kh\u00e1c.<\/p>\n<\/td>\n
\nM\u1ed9t Ph\u00f2ng ban c\u00f3 nhi\u1ec1u Nh\u00e2n vi\u00ean.<\/p>\n<\/td>\n<\/tr>\n
\n\nNhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u (M:N)<\/p>\n<\/td>\n
\nNhi\u1ec1u th\u1ec3 hi\u1ec7n li\u00ean k\u1ebft v\u1edbi nhi\u1ec1u th\u1ec3 hi\u1ec7n c\u1ee7a th\u1ef1c th\u1ec3 kh\u00e1c.<\/p>\n<\/td>\n
\nSinh vi\u00ean \u0111\u0103ng k\u00fd nhi\u1ec1u Kh\u00f3a h\u1ecdc; Kh\u00f3a h\u1ecdc c\u00f3 nhi\u1ec1u Sinh vi\u00ean.<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
Hi\u1ec3u v\u1ec1 T\u00ednh b\u1eaft bu\u1ed9c<\/h3>\n
T\u00ednh ch\u1ea5t ch\u1ec9 ra m\u1ed1i quan h\u1ec7 c\u00f3 b\u1eaft bu\u1ed9c hay kh\u00f4ng. \u0110i\u1ec1u n\u00e0y th\u01b0\u1eddng \u0111\u01b0\u1ee3c th\u1ec3 hi\u1ec7n b\u1eb1ng c\u00e1c k\u00fd hi\u1ec7u nh\u01b0 m\u1ed9t thanh \u0111\u1ee9ng ho\u1eb7c m\u1ed9t h\u00ecnh tr\u00f2n.<\/p>\n
\n- \n
T\u00f9y ch\u1ecdn (0):<\/strong> M\u1ed9t th\u1ef1c th\u1ec3 c\u00f3 th\u1ec3 t\u1ed3n t\u1ea1i m\u00e0 kh\u00f4ng c\u1ea7n m\u1ed1i quan h\u1ec7.<\/p>\n<\/li>\n- \n
B\u1eaft bu\u1ed9c (1):<\/strong> M\u1ed9t th\u1ef1c th\u1ec3 ph\u1ea3i tham gia v\u00e0o m\u1ed1i quan h\u1ec7.<\/p>\n<\/li>\n<\/ul>\nV\u00ed d\u1ee5, trong m\u1ed1i quan h\u1ec7 \u201cKh\u00e1ch h\u00e0ng \u0111\u1eb7t \u0111\u01a1n h\u00e0ng\u201d:<\/p>\n
\n- \n
M\u1ed9t Kh\u00e1ch h\u00e0ng ph\u1ea3i<\/em>\u0111\u1eb7t \u00edt nh\u1ea5t m\u1ed9t \u0110\u01a1n h\u00e0ng (b\u1eaft bu\u1ed9c).<\/p>\n<\/li>\n- \n
M\u1ed9t \u0110\u01a1n h\u00e0ng c\u00f3 th\u1ec3<\/em>\u0111\u01b0\u1ee3c \u0111\u1eb7t b\u1edfi m\u1ed9t Kh\u00e1ch tham gia (t\u00f9y ch\u1ecdn \u0111\u1ed1i v\u1edbi Kh\u00e1ch h\u00e0ng).<\/p>\n<\/li>\n<\/ul>\nPhong c\u00e1ch k\u00fd hi\u1ec7u \ud83c\udfa8<\/h2>\n
C\u00f3 nhi\u1ec1u ph\u01b0\u01a1ng ph\u00e1p kh\u00e1c nhau \u0111\u1ec3 v\u1ebd s\u01a1 \u0111\u1ed3 ERD. M\u1eb7c d\u00f9 c\u00e1c kh\u00e1i ni\u1ec7m v\u1eabn gi\u1eef nguy\u00ean, nh\u01b0ng c\u00e1c k\u00fd hi\u1ec7u th\u00ec kh\u00e1c nhau.<\/p>\n
K\u00fd hi\u1ec7u Chen<\/h3>\n
T\u00ean g\u1ecdi theo Peter Chen, ng\u01b0\u1eddi s\u00e1ng t\u1ea1o ra m\u00f4 h\u00ecnh ER. N\u00f3 s\u1eed d\u1ee5ng h\u00ecnh ch\u1eef nh\u1eadt cho c\u00e1c th\u1ef1c th\u1ec3, h\u00ecnh thoi cho c\u00e1c m\u1ed1i quan h\u1ec7 v\u00e0 h\u00ecnh elip cho c\u00e1c thu\u1ed9c t\u00ednh.<\/p>\n
\n- \n
\u01afu \u0111i\u1ec3m:<\/strong> R\u1ea5t r\u00f5 r\u00e0ng v\u1ec1 m\u1ed1i quan h\u1ec7 v\u00e0 thu\u1ed9c t\u00ednh.<\/p>\n<\/li>\n- \n
Nh\u01b0\u1ee3c \u0111i\u1ec3m:<\/strong> C\u00f3 th\u1ec3 tr\u1edf n\u00ean r\u1ed1i r\u1eafm khi h\u1ec7 th\u1ed1ng ph\u1ee9c t\u1ea1p.<\/p>\n<\/li>\n<\/ul>\nK\u00fd hi\u1ec7u Ch\u00e2n chim<\/h3>\n
M\u1ed9t bi\u1ebfn th\u1ec3 c\u1ee7a k\u00fd hi\u1ec7u Bachman. N\u00f3 s\u1eed d\u1ee5ng c\u00e1c \u0111\u01b0\u1eddng th\u1eb3ng v\u1edbi c\u00e1c k\u00fd hi\u1ec7u \u1edf hai \u0111\u1ea7u \u0111\u1ec3 bi\u1ec3u th\u1ecb t\u00ednh b\u1ed9i s\u1ed1.<\/p>\n
\n- \n
\u0110\u01b0\u1eddng \u0111\u01a1n:<\/strong>Bi\u1ec3u th\u1ecb \u201cm\u1ed9t\u201d.<\/p>\n<\/li>\n- \n
Ch\u00e2n chim (ba nh\u00e1nh):<\/strong>Bi\u1ec3u th\u1ecb \u201cnhi\u1ec1u\u201d.<\/p>\n<\/li>\n- \n
H\u00ecnh tr\u00f2n:<\/strong>Bi\u1ec3u th\u1ecb \u201ct\u00f9y ch\u1ecdn\u201d.<\/p>\n<\/li>\n- \n
Thanh \u0111\u1ee9ng:<\/strong>Bi\u1ec3u th\u1ecb \u201cb\u1eaft bu\u1ed9c\u201d.<\/p>\n<\/li>\n<\/ul>\nS\u01a1 \u0111\u1ed3 l\u1edbp UML<\/h3>\n
C\u00e1c s\u01a1 \u0111\u1ed3 Ng\u00f4n ng\u1eef m\u00f4 h\u00ecnh h\u00f3a th\u1ed1ng nh\u1ea5t th\u01b0\u1eddng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng trong k\u1ef9 thu\u1eadt ph\u1ea7n m\u1ec1m. Ch\u00fang tr\u00f4ng gi\u1ed1ng nh\u01b0 c\u00e1c s\u01a1 \u0111\u1ed3 ERD nh\u01b0ng bao g\u1ed3m nhi\u1ec1u kh\u00e1i ni\u1ec7m h\u01b0\u1edbng \u0111\u1ed1i t\u01b0\u1ee3ng h\u01a1n nh\u01b0 k\u1ebf th\u1eeba v\u00e0 ph\u01b0\u01a1ng th\u1ee9c.<\/p>\n
\n\n \n\n\nT\u00ednh n\u0103ng<\/p>\n<\/th>\n
\nK\u00fd hi\u1ec7u Chen<\/p>\n<\/th>\n
\nCh\u00e2n chim<\/p>\n<\/th>\n<\/tr>\n
\n\nH\u00ecnh d\u1ea1ng th\u1ef1c th\u1ec3<\/p>\n<\/td>\n
\nH\u00ecnh ch\u1eef nh\u1eadt<\/p>\n<\/td>\n
\nH\u00ecnh ch\u1eef nh\u1eadt<\/p>\n<\/td>\n<\/tr>\n
\n\nH\u00ecnh d\u1ea1ng m\u1ed1i quan h\u1ec7<\/p>\n<\/td>\n
\nH\u00ecnh thoi<\/p>\n<\/td>\n
\n\u0110\u01b0\u1eddng c\u00f3 k\u00fd hi\u1ec7u<\/p>\n<\/td>\n<\/tr>\n
\n\nH\u00ecnh d\u1ea1ng thu\u1ed9c t\u00ednh<\/p>\n<\/td>\n
\nH\u00ecnh elip<\/p>\n<\/td>\n
\nDanh s\u00e1ch v\u0103n b\u1ea3n<\/p>\n<\/td>\n<\/tr>\n
\n\n\u0110\u1ed9 d\u1ec5 \u0111\u1ecdc<\/p>\n<\/td>\n
\nCao cho c\u00e1c kh\u00e1i ni\u1ec7m<\/p>\n<\/td>\n
\nCao cho tri\u1ec3n khai<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
Thi\u1ebft k\u1ebf l\u01b0\u1ee3c \u0111\u1ed3 c\u01a1 s\u1edf d\u1eef li\u1ec7u \ud83d\udee0\ufe0f<\/h2>\n
Vi\u1ec7c t\u1ea1o s\u01a1 \u0111\u1ed3 ERD kh\u00f4ng ch\u1ec9 \u0111\u01a1n thu\u1ea7n l\u00e0 v\u1ebd c\u00e1c h\u00ecnh d\u1ea1ng. N\u00f3 \u0111\u00f2i h\u1ecfi t\u01b0 duy logic v\u1ec1 c\u00e1ch d\u1eef li\u1ec7u di chuy\u1ec3n v\u00e0 t\u01b0\u01a1ng t\u00e1c v\u1edbi nhau. H\u00e3y tu\u00e2n theo c\u00e1c b\u01b0\u1edbc sau \u0111\u1ec3 x\u00e2y d\u1ef1ng n\u1ec1n t\u1ea3ng v\u1eefng ch\u1eafc.<\/p>\n
B\u01b0\u1edbc 1: X\u00e1c \u0111\u1ecbnh c\u00e1c th\u1ef1c th\u1ec3<\/h3>\n
H\u00e3y xem x\u00e9t c\u00e1c y\u00eau c\u1ea7u kinh doanh. Nh\u1eefng \u0111\u1ed1i t\u01b0\u1ee3ng n\u00e0o c\u1ea7n \u0111\u01b0\u1ee3c theo d\u00f5i? H\u00e3y li\u1ec7t k\u00ea ch\u00fang ra.<\/p>\n
\n- \n
Nh\u1eefng ai l\u00e0 ng\u01b0\u1eddi tham gia? (Ng\u01b0\u1eddi d\u00f9ng, Kh\u00e1ch h\u00e0ng, Nh\u00e2n vi\u00ean)<\/p>\n<\/li>\n
- \n
Nh\u1eefng m\u1eb7t h\u00e0ng n\u00e0o? (S\u1ea3n ph\u1ea9m, \u0110\u01a1n h\u00e0ng, H\u00f3a \u0111\u01a1n)<\/p>\n<\/li>\n
- \n
Nh\u1eefng \u0111\u1ecba \u0111i\u1ec3m n\u00e0o? (Kho h\u00e0ng, Chi nh\u00e1nh)<\/p>\n<\/li>\n<\/ul>\n
B\u01b0\u1edbc 2: X\u00e1c \u0111\u1ecbnh thu\u1ed9c t\u00ednh<\/h3>\n
V\u1edbi m\u1ed7i th\u1ef1c th\u1ec3, h\u00e3y li\u1ec7t k\u00ea c\u00e1c chi ti\u1ebft c\u1ea7n thi\u1ebft. X\u00e1c \u0111\u1ecbnh nh\u1eefng thu\u1ed9c t\u00ednh n\u00e0o l\u00e0 \u0111\u1ecbnh danh duy nh\u1ea5t.<\/p>\n
\n- \n
\u0110\u1ed1i v\u1edbi \u201cS\u1ea3n ph\u1ea9m\u201d: T\u00ean, Gi\u00e1, SKU, M\u00f4 t\u1ea3.<\/p>\n<\/li>\n
- \n
\u0110\u1ed1i v\u1edbi \u201cNg\u01b0\u1eddi d\u00f9ng\u201d: T\u00ean \u0111\u0103ng nh\u1eadp, Email, M\u00e3 b\u0103m m\u1eadt kh\u1ea9u, Ng\u00e0y tham gia.<\/p>\n<\/li>\n<\/ul>\n
B\u01b0\u1edbc 3: X\u00e1c \u0111\u1ecbnh m\u1ed1i quan h\u1ec7<\/h3>\n
C\u00e1c th\u1ef1c th\u1ec3 k\u1ebft n\u1ed1i v\u1edbi nhau nh\u01b0 th\u1ebf n\u00e0o? H\u00e3y \u0111\u1eb7t c\u00e1c c\u00e2u h\u1ecfi nh\u01b0: \u201cM\u1ed9t s\u1ea3n ph\u1ea9m c\u00f3 th\u1ec3 t\u1ed3n t\u1ea1i m\u00e0 kh\u00f4ng c\u1ea7n danh m\u1ee5c kh\u00f4ng?\u201d hay \u201cM\u1ed9t \u0111\u01a1n h\u00e0ng c\u00f3 th\u1ec3 t\u1ed3n t\u1ea1i m\u00e0 kh\u00f4ng c\u1ea7n kh\u00e1ch h\u00e0ng kh\u00f4ng?\u201d<\/p>\n
B\u01b0\u1edbc 4: X\u00e1c \u0111\u1ecbnh t\u00ednh cardinality<\/h3>\n
G\u00e1n cardinality \u0111\u00fang cho m\u1ed7i m\u1ed1i quan h\u1ec7. H\u00e3y ch\u00ednh x\u00e1c v\u1ec1 c\u00e1c r\u00e0ng bu\u1ed9c b\u1eaft bu\u1ed9c so v\u1edbi t\u00f9y ch\u1ecdn.<\/p>\n
B\u01b0\u1edbc 5: Chu\u1ea9n h\u00f3a d\u1eef li\u1ec7u<\/h3>\n
Chu\u1ea9n h\u00f3a l\u00e0 qu\u00e1 tr\u00ecnh t\u1ed5 ch\u1ee9c d\u1eef li\u1ec7u \u0111\u1ec3 gi\u1ea3m thi\u1ec3u s\u1ef1 tr\u00f9ng l\u1eb7p. M\u1eb7c d\u00f9 ERD th\u1ec3 hi\u1ec7n c\u00e1c m\u1ed1i quan h\u1ec7, nh\u01b0ng l\u01b0\u1ee3c \u0111\u1ed3 n\u1ec1n t\u1ea3ng ph\u1ea3i tu\u00e2n theo c\u00e1c quy t\u1eafc chu\u1ea9n h\u00f3a.<\/p>\n
\n- \n
D\u1ea1ng chu\u1ea9n th\u1ee9 nh\u1ea5t (1NF):<\/strong>\u0110\u1ea3m b\u1ea3o c\u00e1c gi\u00e1 tr\u1ecb nguy\u00ean t\u1eed. Kh\u00f4ng c\u00f3 danh s\u00e1ch trong m\u1ed9t \u00f4 duy nh\u1ea5t.<\/p>\n<\/li>\n- \n
D\u1ea1ng chu\u1ea9n th\u1ee9 hai (2NF):<\/strong>Lo\u1ea1i b\u1ecf c\u00e1c ph\u1ee5 thu\u1ed9c ri\u00eang ph\u1ea7n. T\u1ea5t c\u1ea3 c\u00e1c thu\u1ed9c t\u00ednh ph\u1ea3i ph\u1ee5 thu\u1ed9c v\u00e0o to\u00e0n b\u1ed9 kh\u00f3a ch\u00ednh.<\/p>\n<\/li>\n- \n
D\u1ea1ng chu\u1ea9n th\u1ee9 ba (3NF):<\/strong>Lo\u1ea1i b\u1ecf c\u00e1c ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u. C\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng n\u00ean ph\u1ee5 thu\u1ed9c v\u00e0o c\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng ph\u1ea3i kh\u00f3a kh\u00e1c.<\/p>\n<\/li>\n<\/ul>\nNh\u1eefng sai l\u1ea7m ph\u1ed5 bi\u1ebfn c\u1ea7n tr\u00e1nh \u26a0\ufe0f<\/h2>\n
Ngay c\u1ea3 nh\u1eefng nh\u00e0 thi\u1ebft k\u1ebf c\u00f3 kinh nghi\u1ec7m c\u0169ng m\u1eafc sai l\u1ea7m. Nh\u1eadn th\u1ee9c \u0111\u01b0\u1ee3c nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn s\u1ebd gi\u00fap c\u1ea3i thi\u1ec7n ch\u1ea5t l\u01b0\u1ee3ng s\u01a1 \u0111\u1ed3.<\/p>\n
\n- \n
Chu\u1ea9n h\u00f3a qu\u00e1 m\u1ee9c:<\/strong>T\u1ea1o qu\u00e1 nhi\u1ec1u b\u1ea3ng c\u00f3 th\u1ec3 l\u00e0m ch\u1eadm c\u00e1c truy v\u1ea5n. C\u00e2n b\u1eb1ng gi\u1eefa chu\u1ea9n h\u00f3a v\u00e0 nhu c\u1ea7u hi\u1ec7u su\u1ea5t.<\/p>\n<\/li>\n- \n
B\u1ecf qua ki\u1ec3u d\u1eef li\u1ec7u:<\/strong>ERD l\u00e0 logic, nh\u01b0ng tri\u1ec3n khai y\u00eau c\u1ea7u c\u00e1c ki\u1ec3u d\u1eef li\u1ec7u c\u1ee5 th\u1ec3 (Integer, Varchar, Date).<\/p>\n<\/li>\n- \n
Thi\u1ebfu r\u00e0ng bu\u1ed9c:<\/strong>Kh\u00f4ng \u0111\u00e1nh d\u1ea5u c\u00e1c tr\u01b0\u1eddng b\u1eaft bu\u1ed9c c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn v\u1ea5n \u0111\u1ec1 to\u00e0n v\u1eb9n d\u1eef li\u1ec7u sau n\u00e0y.<\/p>\n<\/li>\n- \n
C\u00e1c m\u1ed1i quan h\u1ec7 ph\u1ee9c t\u1ea1p:<\/strong>Tr\u00e1nh c\u00e1c m\u1ed1i quan h\u1ec7 nhi\u1ec1u-\u0111a m\u00e0 kh\u00f4ng c\u00f3 b\u1ea3ng li\u00ean k\u1ebft. M\u1ed9t m\u1ed1i quan h\u1ec7 nhi\u1ec1u-\u0111a ng\u1ee5 \u00fd m\u1ed9t th\u1ef1c th\u1ec3 th\u1ee9 ba.<\/p>\n<\/li>\n<\/ul>\nV\u00ed d\u1ee5: Gi\u1ea3i quy\u1ebft m\u1ed1i quan h\u1ec7 nhi\u1ec1u-\u0111a<\/h3>\n
N\u1ebfu b\u1ea1n c\u00f3 \u2018Sinh vi\u00ean\u2019 v\u00e0 \u2018Kh\u00f3a h\u1ecdc\u2019, b\u1ea1n kh\u00f4ng th\u1ec3 k\u1ebft n\u1ed1i ch\u00fang tr\u1ef1c ti\u1ebfp b\u1eb1ng m\u1ed9t \u0111\u01b0\u1eddng duy nh\u1ea5t. B\u1ea1n ph\u1ea3i gi\u1edbi thi\u1ec7u m\u1ed9t th\u1ef1c th\u1ec3 \u2018\u0110\u0103ng k\u00fd\u2019.<\/p>\n
\n- \n
Sinh vi\u00ean (1) \u2014- (N) \u0110\u0103ng k\u00fd<\/p>\n<\/li>\n
- \n
Kh\u00f3a h\u1ecdc (1) \u2014- (N) \u0110\u0103ng k\u00fd<\/p>\n<\/li>\n<\/ul>\n
\u0110i\u1ec1u n\u00e0y t\u1ea1o ra hai m\u1ed1i quan h\u1ec7 m\u1ed9t-\u0111a, m\u00e0 c\u01a1 s\u1edf d\u1eef li\u1ec7u x\u1eed l\u00fd hi\u1ec7u qu\u1ea3 h\u01a1n.<\/p>\n
C\u00e1c th\u1ef1c h\u00e0nh t\u1ed1t nh\u1ea5t cho b\u1ea3o tr\u00ec \ud83d\udcdd<\/h2>\n
M\u1ed9t khi s\u01a1 \u0111\u1ed3 \u0111\u01b0\u1ee3c t\u1ea1o, n\u00f3 tr\u1edf th\u00e0nh t\u00e0i li\u1ec7u s\u1ed1ng. N\u00f3 ph\u1ea3i ph\u00e1t tri\u1ec3n theo s\u1ef1 ph\u00e1t tri\u1ec3n c\u1ee7a h\u1ec7 th\u1ed1ng.<\/p>\n
\n- \n
Ki\u1ec3m so\u00e1t phi\u00ean b\u1ea3n:<\/strong>Theo d\u00f5i c\u00e1c thay \u0111\u1ed5i \u0111\u1ed1i v\u1edbi l\u01b0\u1ee3c \u0111\u1ed3 theo th\u1eddi gian.<\/p>\n<\/li>\n- \n
C\u00e1c bu\u1ed5i xem x\u00e9t:<\/strong> Th\u01b0\u1eddng xuy\u00ean xem x\u00e9t s\u01a1 \u0111\u1ed3 c\u00f9ng v\u1edbi \u0111\u1ed9i ph\u00e1t tri\u1ec3n.<\/p>\n<\/li>\n- \n
T\u00ean g\u1ecdi nh\u1ea5t qu\u00e1n:<\/strong> S\u1eed d\u1ee5ng c\u00e1c quy \u01b0\u1edbc \u0111\u1eb7t t\u00ean r\u00f5 r\u00e0ng v\u00e0 nh\u1ea5t qu\u00e1n cho c\u00e1c b\u1ea3ng v\u00e0 c\u1ed9t.<\/p>\n<\/li>\n- \n
T\u00e0i li\u1ec7u:<\/strong> Th\u00eam ghi ch\u00fa gi\u1ea3i th\u00edch logic ph\u1ee9c t\u1ea1p ho\u1eb7c c\u00e1c quy t\u1eafc kinh doanh tr\u1ef1c ti\u1ebfp tr\u00ean s\u01a1 \u0111\u1ed3.<\/p>\n<\/li>\n<\/ul>\nK\u1ebft lu\u1eadn \ud83c\udfc1<\/h2>\n
Th\u00e0nh th\u1ea1o s\u01a1 \u0111\u1ed3 Th\u1ef1c th\u1ec3 – Quan h\u1ec7 l\u00e0 k\u1ef9 n\u0103ng quan tr\u1ecdng \u0111\u1ed1i v\u1edbi thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u. N\u00f3 t\u1ea1o ra s\u1ef1 k\u1ebft n\u1ed1i gi\u1eefa c\u00e1c y\u00eau c\u1ea7u kinh doanh tr\u1eebu t\u01b0\u1ee3ng v\u00e0 vi\u1ec7c tri\u1ec3n khai k\u1ef9 thu\u1eadt c\u1ee5 th\u1ec3. B\u1eb1ng c\u00e1ch hi\u1ec3u r\u00f5 c\u00e1c th\u1ef1c th\u1ec3, thu\u1ed9c t\u00ednh v\u00e0 m\u1ed1i quan h\u1ec7, b\u1ea1n c\u00f3 th\u1ec3 x\u00e2y d\u1ef1ng c\u00e1c h\u1ec7 th\u1ed1ng c\u00f3 kh\u1ea3 n\u0103ng m\u1edf r\u1ed9ng, d\u1ec5 b\u1ea3o tr\u00ec v\u00e0 hi\u1ec7u qu\u1ea3.<\/p>\n
H\u00e3y nh\u1edb r\u1eb1ng s\u1ef1 r\u00f5 r\u00e0ng l\u00e0 m\u1ee5c ti\u00eau. M\u1ed9t s\u01a1 \u0111\u1ed3 c\u1ea7n ph\u1ea3i d\u1ec5 \u0111\u1ecdc \u0111\u1ed1i v\u1edbi b\u1ea5t k\u1ef3 ai tham gia d\u1ef1 \u00e1n. S\u1eed d\u1ee5ng c\u00e1c k\u00fd hi\u1ec7u chu\u1ea9n, tu\u00e2n th\u1ee7 c\u00e1c quy t\u1eafc v\u1ec1 c\u1ea5p \u0111\u1ed9, v\u00e0 lu\u00f4n \u01b0u ti\u00ean t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u. V\u1edbi th\u1ef1c h\u00e0nh th\u01b0\u1eddng xuy\u00ean, vi\u1ec7c t\u1ea1o ra nh\u1eefng h\u01b0\u1edbng d\u1eabn tr\u1ef1c quan n\u00e0y s\u1ebd tr\u1edf th\u00e0nh m\u1ed9t ph\u1ea7n t\u1ef1 nhi\u00ean trong quy tr\u00ecnh l\u00e0m vi\u1ec7c c\u1ee7a b\u1ea1n.<\/p>\n","protected":false},"excerpt":{"rendered":"
S\u01a1 \u0111\u1ed3 Th\u1ef1c th\u1ec3 – Quan h\u1ec7, th\u01b0\u1eddng \u0111\u01b0\u1ee3c vi\u1ebft t\u1eaft l\u00e0 ERD, \u0111\u00f3ng vai tr\u00f2 nh\u01b0 b\u1ea3n v\u1ebd thi\u1ebft k\u1ebf cho c\u01a1 s\u1edf d\u1eef li\u1ec7u. N\u00f3 cung c\u1ea5p m\u1ed9t…<\/p>\n","protected":false},"author":1,"featured_media":1686,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_yoast_wpseo_title":"C\u00e1c nguy\u00ean t\u1eafc c\u01a1 b\u1ea3n c\u1ee7a s\u01a1 \u0111\u1ed3 Th\u1ef1c th\u1ec3 - Quan h\u1ec7: H\u01b0\u1edbng d\u1eabn tr\u1ef1c quan cho ng\u01b0\u1eddi m\u1edbi b\u1eaft \u0111\u1ea7u \ud83d\udcca","_yoast_wpseo_metadesc":"H\u1ecdc c\u00e1c ki\u1ebfn th\u1ee9c c\u01a1 b\u1ea3n v\u1ec1 ERD, k\u00fd hi\u1ec7u v\u00e0 c\u1ea5p \u0111\u1ed9. M\u1ed9t h\u01b0\u1edbng d\u1eabn tr\u1ef1c quan \u0111\u1ea7y \u0111\u1ee7 d\u00e0nh cho ng\u01b0\u1eddi m\u1edbi b\u1eaft \u0111\u1ea7u thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u. Kh\u00f4ng c\u1ea7n ph\u1ea7n m\u1ec1m. \ud83d\uddc3\ufe0f","fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[86],"tags":[82,85],"class_list":["post-1685","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-erd","tag-academic","tag-erd"],"yoast_head":"\n
C\u00e1c nguy\u00ean t\u1eafc c\u01a1 b\u1ea3n c\u1ee7a s\u01a1 \u0111\u1ed3 Th\u1ef1c th\u1ec3 - Quan h\u1ec7: H\u01b0\u1edbng d\u1eabn tr\u1ef1c quan cho ng\u01b0\u1eddi m\u1edbi b\u1eaft \u0111\u1ea7u \ud83d\udcca<\/title>\n<meta name=\"description\" content=\"H\u1ecdc c\u00e1c ki\u1ebfn th\u1ee9c c\u01a1 b\u1ea3n v\u1ec1 ERD, k\u00fd hi\u1ec7u v\u00e0 c\u1ea5p \u0111\u1ed9. M\u1ed9t h\u01b0\u1edbng d\u1eabn tr\u1ef1c quan \u0111\u1ea7y \u0111\u1ee7 d\u00e0nh cho ng\u01b0\u1eddi m\u1edbi b\u1eaft \u0111\u1ea7u thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u. 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M\u1ed9t h\u01b0\u1edbng d\u1eabn tr\u1ef1c quan \u0111\u1ea7y \u0111\u1ee7 d\u00e0nh cho ng\u01b0\u1eddi m\u1edbi b\u1eaft \u0111\u1ea7u thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u. 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R\u00f5 r\u00e0ng v\u1ec1 m\u1eb7t tr\u1ef1c quan:<\/strong>C\u00e1c c\u1ea5u tr\u00fac d\u1eef li\u1ec7u ph\u1ee9c t\u1ea1p tr\u1edf n\u00ean d\u1ec5 hi\u1ec3u h\u01a1n khi \u0111\u01b0\u1ee3c v\u1ebd ra.<\/p>\n<\/li>\n Ti\u00eau chu\u1ea9n h\u00f3a:<\/strong>Cung c\u1ea5p m\u1ed9t ng\u00f4n ng\u1eef chung cho c\u00e1c \u0111\u1ed9i k\u1ef9 thu\u1eadt v\u00e0 kh\u00f4ng k\u1ef9 thu\u1eadt.<\/p>\n<\/li>\n Hi\u1ec7u qu\u1ea3:<\/strong>Ph\u00e1t hi\u1ec7n s\u1edbm c\u00e1c v\u1ea5n \u0111\u1ec1 ti\u1ec1m \u1ea9n nh\u01b0 d\u1eef li\u1ec7u tr\u00f9ng l\u1eb7p.<\/p>\n<\/li>\n T\u00e0i li\u1ec7u tham kh\u1ea3o:<\/strong>L\u00e0 t\u00e0i li\u1ec7u tham kh\u1ea3o cho vi\u1ec7c b\u1ea3o tr\u00ec v\u00e0 m\u1edf r\u1ed9ng trong t\u01b0\u01a1ng lai.<\/p>\n<\/li>\n<\/ul>\n M\u1ed7i s\u01a1 \u0111\u1ed3 bao g\u1ed3m ba kh\u1ed1i x\u00e2y d\u1ef1ng c\u01a1 b\u1ea3n. Vi\u1ec7c hi\u1ec3u r\u00f5 nh\u1eefng kh\u1ed1i n\u00e0y l\u00e0 b\u01b0\u1edbc \u0111\u1ea7u ti\u00ean \u0111\u1ec3 t\u1ea1o ra m\u1ed9t l\u01b0\u1ee3c \u0111\u1ed3 v\u1eefng ch\u1eafc.<\/p>\n M\u1ed9t th\u1ef1c th\u1ec3 \u0111\u1ea1i di\u1ec7n cho m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng ho\u1eb7c kh\u00e1i ni\u1ec7m trong th\u1ebf gi\u1edbi th\u1ef1c m\u00e0 d\u1eef li\u1ec7u c\u1ea7n \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef. Trong ng\u1eef c\u1ea3nh c\u01a1 s\u1edf d\u1eef li\u1ec7u, m\u1ed9t th\u1ef1c th\u1ec3 th\u01b0\u1eddng t\u01b0\u01a1ng \u1ee9ng v\u1edbi m\u1ed9t b\u1ea3ng.<\/p>\n Th\u1ef1c th\u1ec3 m\u1ea1nh:<\/strong>Ch\u00fang t\u1ed3n t\u1ea1i \u0111\u1ed9c l\u1eadp. V\u00ed d\u1ee5, b\u1ea3ng \u201cKh\u00e1ch h\u00e0ng\u201d t\u1ed3n t\u1ea1i d\u00f9 kh\u00f4ng ph\u1ee5 thu\u1ed9c v\u00e0o c\u00e1c b\u1ea3ng kh\u00e1c.<\/p>\n<\/li>\n Th\u1ef1c th\u1ec3 y\u1ebfu:<\/strong>Ch\u00fang ph\u1ee5 thu\u1ed9c v\u00e0o m\u1ed9t th\u1ef1c th\u1ec3 kh\u00e1c \u0111\u1ec3 t\u1ed3n t\u1ea1i. M\u1ed9t \u201cChi ti\u1ebft h\u00f3a \u0111\u01a1n\u201d c\u00f3 th\u1ec3 kh\u00f4ng c\u00f3 \u00fd ngh\u0129a n\u1ebfu kh\u00f4ng c\u00f3 \u201cH\u00f3a \u0111\u01a1n\u201d.<\/p>\n<\/li>\n<\/ul>\n C\u00e1c th\u1ef1c th\u1ec3 th\u01b0\u1eddng \u0111\u01b0\u1ee3c bi\u1ec3u di\u1ec5n b\u1eb1ng h\u00ecnh ch\u1eef nh\u1eadt. T\u00ean b\u00ean trong h\u00ecnh ch\u1eef nh\u1eadt l\u00e0 s\u1ed1 nhi\u1ec1u, cho th\u1ea5y b\u1ea3ng m\u00e0 n\u00f3 \u0111\u1ea1i di\u1ec7n.<\/p>\n C\u00e1c thu\u1ed9c t\u00ednh m\u00f4 t\u1ea3 c\u00e1c thu\u1ed9c t\u00ednh ho\u1eb7c \u0111\u1eb7c \u0111i\u1ec3m c\u1ee7a m\u1ed9t th\u1ef1c th\u1ec3. Ch\u00fang t\u01b0\u01a1ng \u1ee9ng v\u1edbi c\u00e1c c\u1ed9t trong m\u1ed9t b\u1ea3ng c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/p>\n Kh\u00f3a ch\u00ednh:<\/strong>M\u1ed9t \u0111\u1ecbnh danh duy nh\u1ea5t cho m\u1ed7i b\u1ea3n ghi. V\u1edbi kh\u00e1ch h\u00e0ng, \u0111i\u1ec1u n\u00e0y c\u00f3 th\u1ec3 l\u00e0 \u201cM\u00e3Kh\u00e1chH\u00e0ng\u201d.<\/p>\n<\/li>\n Kh\u00f3a ngo\u1ea1i:<\/strong>M\u1ed9t tr\u01b0\u1eddng li\u00ean k\u1ebft \u0111\u1ebfn kh\u00f3a ch\u00ednh c\u1ee7a m\u1ed9t b\u1ea3ng kh\u00e1c.<\/p>\n<\/li>\n Thu\u1ed9c t\u00ednh \u0111\u01a1n gi\u1ea3n:<\/strong> M\u1ed9t gi\u00e1 tr\u1ecb kh\u00f4ng th\u1ec3 chia t\u00e1ch, v\u00ed d\u1ee5 nh\u01b0 m\u1ed9t \u201cS\u1ed1 \u0111i\u1ec7n tho\u1ea1i\u201d.<\/p>\n<\/li>\n Thu\u1ed9c t\u00ednh h\u1ee3p th\u00e0nh:<\/strong> M\u1ed9t thu\u1ed9c t\u00ednh c\u00f3 th\u1ec3 chia th\u00e0nh c\u00e1c ph\u1ea7n nh\u1ecf h\u01a1n, v\u00ed d\u1ee5 nh\u01b0 \u201c\u0110\u1ecba ch\u1ec9\u201d (\u0110\u01b0\u1eddng, Th\u00e0nh ph\u1ed1, M\u00e3 b\u01b0u ch\u00ednh).<\/p>\n<\/li>\n Thu\u1ed9c t\u00ednh nhi\u1ec1u gi\u00e1 tr\u1ecb:<\/strong> M\u1ed9t thu\u1ed9c t\u00ednh c\u00f3 th\u1ec3 ch\u1ee9a nhi\u1ec1u gi\u00e1 tr\u1ecb, v\u00ed d\u1ee5 nh\u01b0 \u201cEmailAddresses\u201d.<\/p>\n<\/li>\n Thu\u1ed9c t\u00ednh suy ra:<\/strong> M\u1ed9t gi\u00e1 tr\u1ecb \u0111\u01b0\u1ee3c t\u00ednh to\u00e1n t\u1eeb c\u00e1c thu\u1ed9c t\u00ednh kh\u00e1c, v\u00ed d\u1ee5 nh\u01b0 \u201cTu\u1ed5i\u201d \u0111\u01b0\u1ee3c suy ra t\u1eeb \u201cNg\u00e0y sinh\u201d.<\/p>\n<\/li>\n<\/ul>\n C\u00e1c m\u1ed1i quan h\u1ec7 x\u00e1c \u0111\u1ecbnh c\u00e1ch c\u00e1c th\u1ef1c th\u1ec3 t\u01b0\u01a1ng t\u00e1c v\u1edbi nhau. Ch\u00fang m\u00f4 t\u1ea3 c\u00e1c k\u1ebft n\u1ed1i gi\u1eefa c\u00e1c \u0111i\u1ec3m d\u1eef li\u1ec7u.<\/p>\n M\u1ed1i quan h\u1ec7 li\u00ean k\u1ebft:<\/strong> Ch\u00fang k\u1ebft n\u1ed1i hai ho\u1eb7c nhi\u1ec1u th\u1ef1c th\u1ec3.<\/p>\n<\/li>\n M\u1ed1i quan h\u1ec7 x\u00e1c \u0111\u1ecbnh:<\/strong> Ch\u00fang x\u00e1c \u0111\u1ecbnh s\u1ef1 t\u1ed3n t\u1ea1i c\u1ee7a m\u1ed9t th\u1ef1c th\u1ec3 y\u1ebfu.<\/p>\n<\/li>\n<\/ul>\n Trong s\u01a1 \u0111\u1ed3, c\u00e1c m\u1ed1i quan h\u1ec7 th\u01b0\u1eddng \u0111\u01b0\u1ee3c bi\u1ec3u di\u1ec5n b\u1eb1ng h\u00ecnh thoi ho\u1eb7c c\u00e1c \u0111\u01b0\u1eddng n\u1ed1i gi\u1eefa c\u00e1c th\u1ef1c th\u1ec3. Lo\u1ea1i m\u1ed1i quan h\u1ec7 \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh b\u1edfi t\u00ednh cardinality.<\/p>\n Cardinality x\u00e1c \u0111\u1ecbnh s\u1ed1 l\u01b0\u1ee3ng th\u1ec3 hi\u1ec7n c\u1ee7a m\u1ed9t th\u1ef1c th\u1ec3 c\u00f3 th\u1ec3 ho\u1eb7c ph\u1ea3i li\u00ean k\u1ebft v\u1edbi m\u1ed7i th\u1ec3 hi\u1ec7n c\u1ee7a th\u1ef1c th\u1ec3 kh\u00e1c. T\u00ednh b\u1eaft bu\u1ed9c x\u00e1c \u0111\u1ecbnh m\u1ed1i quan h\u1ec7 l\u00e0 b\u1eaft bu\u1ed9c hay t\u00f9y ch\u1ecdn.<\/p>\n Cardinality<\/p>\n<\/th>\n M\u00f4 t\u1ea3<\/p>\n<\/th>\n V\u00ed d\u1ee5 t\u00ecnh hu\u1ed1ng<\/p>\n<\/th>\n<\/tr>\n M\u1ed9t-\u0111\u1ed1i-m\u1ed9t (1:1)<\/p>\n<\/td>\n M\u1ed9t th\u1ec3 hi\u1ec7n li\u00ean k\u1ebft v\u1edbi \u0111\u00fang m\u1ed9t th\u1ec3 hi\u1ec7n kh\u00e1c.<\/p>\n<\/td>\n M\u1ed9t Ng\u01b0\u1eddi c\u00f3 m\u1ed9t H\u1ed9 chi\u1ebfu.<\/p>\n<\/td>\n<\/tr>\n M\u1ed9t-\u0111\u1ed1i-nhi\u1ec1u (1:N)<\/p>\n<\/td>\n M\u1ed9t th\u1ec3 hi\u1ec7n li\u00ean k\u1ebft v\u1edbi nhi\u1ec1u th\u1ec3 hi\u1ec7n c\u1ee7a th\u1ef1c th\u1ec3 kh\u00e1c.<\/p>\n<\/td>\n M\u1ed9t Ph\u00f2ng ban c\u00f3 nhi\u1ec1u Nh\u00e2n vi\u00ean.<\/p>\n<\/td>\n<\/tr>\n Nhi\u1ec1u-\u0111\u1ed1i-nhi\u1ec1u (M:N)<\/p>\n<\/td>\n Nhi\u1ec1u th\u1ec3 hi\u1ec7n li\u00ean k\u1ebft v\u1edbi nhi\u1ec1u th\u1ec3 hi\u1ec7n c\u1ee7a th\u1ef1c th\u1ec3 kh\u00e1c.<\/p>\n<\/td>\n Sinh vi\u00ean \u0111\u0103ng k\u00fd nhi\u1ec1u Kh\u00f3a h\u1ecdc; Kh\u00f3a h\u1ecdc c\u00f3 nhi\u1ec1u Sinh vi\u00ean.<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n T\u00ednh ch\u1ea5t ch\u1ec9 ra m\u1ed1i quan h\u1ec7 c\u00f3 b\u1eaft bu\u1ed9c hay kh\u00f4ng. \u0110i\u1ec1u n\u00e0y th\u01b0\u1eddng \u0111\u01b0\u1ee3c th\u1ec3 hi\u1ec7n b\u1eb1ng c\u00e1c k\u00fd hi\u1ec7u nh\u01b0 m\u1ed9t thanh \u0111\u1ee9ng ho\u1eb7c m\u1ed9t h\u00ecnh tr\u00f2n.<\/p>\n T\u00f9y ch\u1ecdn (0):<\/strong> M\u1ed9t th\u1ef1c th\u1ec3 c\u00f3 th\u1ec3 t\u1ed3n t\u1ea1i m\u00e0 kh\u00f4ng c\u1ea7n m\u1ed1i quan h\u1ec7.<\/p>\n<\/li>\n B\u1eaft bu\u1ed9c (1):<\/strong> M\u1ed9t th\u1ef1c th\u1ec3 ph\u1ea3i tham gia v\u00e0o m\u1ed1i quan h\u1ec7.<\/p>\n<\/li>\n<\/ul>\n V\u00ed d\u1ee5, trong m\u1ed1i quan h\u1ec7 \u201cKh\u00e1ch h\u00e0ng \u0111\u1eb7t \u0111\u01a1n h\u00e0ng\u201d:<\/p>\n M\u1ed9t Kh\u00e1ch h\u00e0ng ph\u1ea3i<\/em>\u0111\u1eb7t \u00edt nh\u1ea5t m\u1ed9t \u0110\u01a1n h\u00e0ng (b\u1eaft bu\u1ed9c).<\/p>\n<\/li>\n M\u1ed9t \u0110\u01a1n h\u00e0ng c\u00f3 th\u1ec3<\/em>\u0111\u01b0\u1ee3c \u0111\u1eb7t b\u1edfi m\u1ed9t Kh\u00e1ch tham gia (t\u00f9y ch\u1ecdn \u0111\u1ed1i v\u1edbi Kh\u00e1ch h\u00e0ng).<\/p>\n<\/li>\n<\/ul>\n C\u00f3 nhi\u1ec1u ph\u01b0\u01a1ng ph\u00e1p kh\u00e1c nhau \u0111\u1ec3 v\u1ebd s\u01a1 \u0111\u1ed3 ERD. M\u1eb7c d\u00f9 c\u00e1c kh\u00e1i ni\u1ec7m v\u1eabn gi\u1eef nguy\u00ean, nh\u01b0ng c\u00e1c k\u00fd hi\u1ec7u th\u00ec kh\u00e1c nhau.<\/p>\n T\u00ean g\u1ecdi theo Peter Chen, ng\u01b0\u1eddi s\u00e1ng t\u1ea1o ra m\u00f4 h\u00ecnh ER. N\u00f3 s\u1eed d\u1ee5ng h\u00ecnh ch\u1eef nh\u1eadt cho c\u00e1c th\u1ef1c th\u1ec3, h\u00ecnh thoi cho c\u00e1c m\u1ed1i quan h\u1ec7 v\u00e0 h\u00ecnh elip cho c\u00e1c thu\u1ed9c t\u00ednh.<\/p>\n \u01afu \u0111i\u1ec3m:<\/strong> R\u1ea5t r\u00f5 r\u00e0ng v\u1ec1 m\u1ed1i quan h\u1ec7 v\u00e0 thu\u1ed9c t\u00ednh.<\/p>\n<\/li>\n Nh\u01b0\u1ee3c \u0111i\u1ec3m:<\/strong> C\u00f3 th\u1ec3 tr\u1edf n\u00ean r\u1ed1i r\u1eafm khi h\u1ec7 th\u1ed1ng ph\u1ee9c t\u1ea1p.<\/p>\n<\/li>\n<\/ul>\n M\u1ed9t bi\u1ebfn th\u1ec3 c\u1ee7a k\u00fd hi\u1ec7u Bachman. N\u00f3 s\u1eed d\u1ee5ng c\u00e1c \u0111\u01b0\u1eddng th\u1eb3ng v\u1edbi c\u00e1c k\u00fd hi\u1ec7u \u1edf hai \u0111\u1ea7u \u0111\u1ec3 bi\u1ec3u th\u1ecb t\u00ednh b\u1ed9i s\u1ed1.<\/p>\n \u0110\u01b0\u1eddng \u0111\u01a1n:<\/strong>Bi\u1ec3u th\u1ecb \u201cm\u1ed9t\u201d.<\/p>\n<\/li>\n Ch\u00e2n chim (ba nh\u00e1nh):<\/strong>Bi\u1ec3u th\u1ecb \u201cnhi\u1ec1u\u201d.<\/p>\n<\/li>\n H\u00ecnh tr\u00f2n:<\/strong>Bi\u1ec3u th\u1ecb \u201ct\u00f9y ch\u1ecdn\u201d.<\/p>\n<\/li>\n Thanh \u0111\u1ee9ng:<\/strong>Bi\u1ec3u th\u1ecb \u201cb\u1eaft bu\u1ed9c\u201d.<\/p>\n<\/li>\n<\/ul>\n C\u00e1c s\u01a1 \u0111\u1ed3 Ng\u00f4n ng\u1eef m\u00f4 h\u00ecnh h\u00f3a th\u1ed1ng nh\u1ea5t th\u01b0\u1eddng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng trong k\u1ef9 thu\u1eadt ph\u1ea7n m\u1ec1m. Ch\u00fang tr\u00f4ng gi\u1ed1ng nh\u01b0 c\u00e1c s\u01a1 \u0111\u1ed3 ERD nh\u01b0ng bao g\u1ed3m nhi\u1ec1u kh\u00e1i ni\u1ec7m h\u01b0\u1edbng \u0111\u1ed1i t\u01b0\u1ee3ng h\u01a1n nh\u01b0 k\u1ebf th\u1eeba v\u00e0 ph\u01b0\u01a1ng th\u1ee9c.<\/p>\n T\u00ednh n\u0103ng<\/p>\n<\/th>\n K\u00fd hi\u1ec7u Chen<\/p>\n<\/th>\n Ch\u00e2n chim<\/p>\n<\/th>\n<\/tr>\n H\u00ecnh d\u1ea1ng th\u1ef1c th\u1ec3<\/p>\n<\/td>\n H\u00ecnh ch\u1eef nh\u1eadt<\/p>\n<\/td>\n H\u00ecnh ch\u1eef nh\u1eadt<\/p>\n<\/td>\n<\/tr>\n H\u00ecnh d\u1ea1ng m\u1ed1i quan h\u1ec7<\/p>\n<\/td>\n H\u00ecnh thoi<\/p>\n<\/td>\n \u0110\u01b0\u1eddng c\u00f3 k\u00fd hi\u1ec7u<\/p>\n<\/td>\n<\/tr>\n H\u00ecnh d\u1ea1ng thu\u1ed9c t\u00ednh<\/p>\n<\/td>\n H\u00ecnh elip<\/p>\n<\/td>\n Danh s\u00e1ch v\u0103n b\u1ea3n<\/p>\n<\/td>\n<\/tr>\n \u0110\u1ed9 d\u1ec5 \u0111\u1ecdc<\/p>\n<\/td>\n Cao cho c\u00e1c kh\u00e1i ni\u1ec7m<\/p>\n<\/td>\n Cao cho tri\u1ec3n khai<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Vi\u1ec7c t\u1ea1o s\u01a1 \u0111\u1ed3 ERD kh\u00f4ng ch\u1ec9 \u0111\u01a1n thu\u1ea7n l\u00e0 v\u1ebd c\u00e1c h\u00ecnh d\u1ea1ng. N\u00f3 \u0111\u00f2i h\u1ecfi t\u01b0 duy logic v\u1ec1 c\u00e1ch d\u1eef li\u1ec7u di chuy\u1ec3n v\u00e0 t\u01b0\u01a1ng t\u00e1c v\u1edbi nhau. H\u00e3y tu\u00e2n theo c\u00e1c b\u01b0\u1edbc sau \u0111\u1ec3 x\u00e2y d\u1ef1ng n\u1ec1n t\u1ea3ng v\u1eefng ch\u1eafc.<\/p>\n H\u00e3y xem x\u00e9t c\u00e1c y\u00eau c\u1ea7u kinh doanh. Nh\u1eefng \u0111\u1ed1i t\u01b0\u1ee3ng n\u00e0o c\u1ea7n \u0111\u01b0\u1ee3c theo d\u00f5i? H\u00e3y li\u1ec7t k\u00ea ch\u00fang ra.<\/p>\n Nh\u1eefng ai l\u00e0 ng\u01b0\u1eddi tham gia? (Ng\u01b0\u1eddi d\u00f9ng, Kh\u00e1ch h\u00e0ng, Nh\u00e2n vi\u00ean)<\/p>\n<\/li>\n Nh\u1eefng m\u1eb7t h\u00e0ng n\u00e0o? (S\u1ea3n ph\u1ea9m, \u0110\u01a1n h\u00e0ng, H\u00f3a \u0111\u01a1n)<\/p>\n<\/li>\n Nh\u1eefng \u0111\u1ecba \u0111i\u1ec3m n\u00e0o? (Kho h\u00e0ng, Chi nh\u00e1nh)<\/p>\n<\/li>\n<\/ul>\n V\u1edbi m\u1ed7i th\u1ef1c th\u1ec3, h\u00e3y li\u1ec7t k\u00ea c\u00e1c chi ti\u1ebft c\u1ea7n thi\u1ebft. X\u00e1c \u0111\u1ecbnh nh\u1eefng thu\u1ed9c t\u00ednh n\u00e0o l\u00e0 \u0111\u1ecbnh danh duy nh\u1ea5t.<\/p>\n \u0110\u1ed1i v\u1edbi \u201cS\u1ea3n ph\u1ea9m\u201d: T\u00ean, Gi\u00e1, SKU, M\u00f4 t\u1ea3.<\/p>\n<\/li>\n \u0110\u1ed1i v\u1edbi \u201cNg\u01b0\u1eddi d\u00f9ng\u201d: T\u00ean \u0111\u0103ng nh\u1eadp, Email, M\u00e3 b\u0103m m\u1eadt kh\u1ea9u, Ng\u00e0y tham gia.<\/p>\n<\/li>\n<\/ul>\n C\u00e1c th\u1ef1c th\u1ec3 k\u1ebft n\u1ed1i v\u1edbi nhau nh\u01b0 th\u1ebf n\u00e0o? H\u00e3y \u0111\u1eb7t c\u00e1c c\u00e2u h\u1ecfi nh\u01b0: \u201cM\u1ed9t s\u1ea3n ph\u1ea9m c\u00f3 th\u1ec3 t\u1ed3n t\u1ea1i m\u00e0 kh\u00f4ng c\u1ea7n danh m\u1ee5c kh\u00f4ng?\u201d hay \u201cM\u1ed9t \u0111\u01a1n h\u00e0ng c\u00f3 th\u1ec3 t\u1ed3n t\u1ea1i m\u00e0 kh\u00f4ng c\u1ea7n kh\u00e1ch h\u00e0ng kh\u00f4ng?\u201d<\/p>\n G\u00e1n cardinality \u0111\u00fang cho m\u1ed7i m\u1ed1i quan h\u1ec7. H\u00e3y ch\u00ednh x\u00e1c v\u1ec1 c\u00e1c r\u00e0ng bu\u1ed9c b\u1eaft bu\u1ed9c so v\u1edbi t\u00f9y ch\u1ecdn.<\/p>\n Chu\u1ea9n h\u00f3a l\u00e0 qu\u00e1 tr\u00ecnh t\u1ed5 ch\u1ee9c d\u1eef li\u1ec7u \u0111\u1ec3 gi\u1ea3m thi\u1ec3u s\u1ef1 tr\u00f9ng l\u1eb7p. M\u1eb7c d\u00f9 ERD th\u1ec3 hi\u1ec7n c\u00e1c m\u1ed1i quan h\u1ec7, nh\u01b0ng l\u01b0\u1ee3c \u0111\u1ed3 n\u1ec1n t\u1ea3ng ph\u1ea3i tu\u00e2n theo c\u00e1c quy t\u1eafc chu\u1ea9n h\u00f3a.<\/p>\n D\u1ea1ng chu\u1ea9n th\u1ee9 nh\u1ea5t (1NF):<\/strong>\u0110\u1ea3m b\u1ea3o c\u00e1c gi\u00e1 tr\u1ecb nguy\u00ean t\u1eed. Kh\u00f4ng c\u00f3 danh s\u00e1ch trong m\u1ed9t \u00f4 duy nh\u1ea5t.<\/p>\n<\/li>\n D\u1ea1ng chu\u1ea9n th\u1ee9 hai (2NF):<\/strong>Lo\u1ea1i b\u1ecf c\u00e1c ph\u1ee5 thu\u1ed9c ri\u00eang ph\u1ea7n. T\u1ea5t c\u1ea3 c\u00e1c thu\u1ed9c t\u00ednh ph\u1ea3i ph\u1ee5 thu\u1ed9c v\u00e0o to\u00e0n b\u1ed9 kh\u00f3a ch\u00ednh.<\/p>\n<\/li>\n D\u1ea1ng chu\u1ea9n th\u1ee9 ba (3NF):<\/strong>Lo\u1ea1i b\u1ecf c\u00e1c ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u. C\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng n\u00ean ph\u1ee5 thu\u1ed9c v\u00e0o c\u00e1c thu\u1ed9c t\u00ednh kh\u00f4ng ph\u1ea3i kh\u00f3a kh\u00e1c.<\/p>\n<\/li>\n<\/ul>\n Ngay c\u1ea3 nh\u1eefng nh\u00e0 thi\u1ebft k\u1ebf c\u00f3 kinh nghi\u1ec7m c\u0169ng m\u1eafc sai l\u1ea7m. Nh\u1eadn th\u1ee9c \u0111\u01b0\u1ee3c nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn s\u1ebd gi\u00fap c\u1ea3i thi\u1ec7n ch\u1ea5t l\u01b0\u1ee3ng s\u01a1 \u0111\u1ed3.<\/p>\n Chu\u1ea9n h\u00f3a qu\u00e1 m\u1ee9c:<\/strong>T\u1ea1o qu\u00e1 nhi\u1ec1u b\u1ea3ng c\u00f3 th\u1ec3 l\u00e0m ch\u1eadm c\u00e1c truy v\u1ea5n. C\u00e2n b\u1eb1ng gi\u1eefa chu\u1ea9n h\u00f3a v\u00e0 nhu c\u1ea7u hi\u1ec7u su\u1ea5t.<\/p>\n<\/li>\n B\u1ecf qua ki\u1ec3u d\u1eef li\u1ec7u:<\/strong>ERD l\u00e0 logic, nh\u01b0ng tri\u1ec3n khai y\u00eau c\u1ea7u c\u00e1c ki\u1ec3u d\u1eef li\u1ec7u c\u1ee5 th\u1ec3 (Integer, Varchar, Date).<\/p>\n<\/li>\n Thi\u1ebfu r\u00e0ng bu\u1ed9c:<\/strong>Kh\u00f4ng \u0111\u00e1nh d\u1ea5u c\u00e1c tr\u01b0\u1eddng b\u1eaft bu\u1ed9c c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn v\u1ea5n \u0111\u1ec1 to\u00e0n v\u1eb9n d\u1eef li\u1ec7u sau n\u00e0y.<\/p>\n<\/li>\n C\u00e1c m\u1ed1i quan h\u1ec7 ph\u1ee9c t\u1ea1p:<\/strong>Tr\u00e1nh c\u00e1c m\u1ed1i quan h\u1ec7 nhi\u1ec1u-\u0111a m\u00e0 kh\u00f4ng c\u00f3 b\u1ea3ng li\u00ean k\u1ebft. M\u1ed9t m\u1ed1i quan h\u1ec7 nhi\u1ec1u-\u0111a ng\u1ee5 \u00fd m\u1ed9t th\u1ef1c th\u1ec3 th\u1ee9 ba.<\/p>\n<\/li>\n<\/ul>\n N\u1ebfu b\u1ea1n c\u00f3 \u2018Sinh vi\u00ean\u2019 v\u00e0 \u2018Kh\u00f3a h\u1ecdc\u2019, b\u1ea1n kh\u00f4ng th\u1ec3 k\u1ebft n\u1ed1i ch\u00fang tr\u1ef1c ti\u1ebfp b\u1eb1ng m\u1ed9t \u0111\u01b0\u1eddng duy nh\u1ea5t. B\u1ea1n ph\u1ea3i gi\u1edbi thi\u1ec7u m\u1ed9t th\u1ef1c th\u1ec3 \u2018\u0110\u0103ng k\u00fd\u2019.<\/p>\n Sinh vi\u00ean (1) \u2014- (N) \u0110\u0103ng k\u00fd<\/p>\n<\/li>\n Kh\u00f3a h\u1ecdc (1) \u2014- (N) \u0110\u0103ng k\u00fd<\/p>\n<\/li>\n<\/ul>\n \u0110i\u1ec1u n\u00e0y t\u1ea1o ra hai m\u1ed1i quan h\u1ec7 m\u1ed9t-\u0111a, m\u00e0 c\u01a1 s\u1edf d\u1eef li\u1ec7u x\u1eed l\u00fd hi\u1ec7u qu\u1ea3 h\u01a1n.<\/p>\n M\u1ed9t khi s\u01a1 \u0111\u1ed3 \u0111\u01b0\u1ee3c t\u1ea1o, n\u00f3 tr\u1edf th\u00e0nh t\u00e0i li\u1ec7u s\u1ed1ng. N\u00f3 ph\u1ea3i ph\u00e1t tri\u1ec3n theo s\u1ef1 ph\u00e1t tri\u1ec3n c\u1ee7a h\u1ec7 th\u1ed1ng.<\/p>\n Ki\u1ec3m so\u00e1t phi\u00ean b\u1ea3n:<\/strong>Theo d\u00f5i c\u00e1c thay \u0111\u1ed5i \u0111\u1ed1i v\u1edbi l\u01b0\u1ee3c \u0111\u1ed3 theo th\u1eddi gian.<\/p>\n<\/li>\n C\u00e1c bu\u1ed5i xem x\u00e9t:<\/strong> Th\u01b0\u1eddng xuy\u00ean xem x\u00e9t s\u01a1 \u0111\u1ed3 c\u00f9ng v\u1edbi \u0111\u1ed9i ph\u00e1t tri\u1ec3n.<\/p>\n<\/li>\n T\u00ean g\u1ecdi nh\u1ea5t qu\u00e1n:<\/strong> S\u1eed d\u1ee5ng c\u00e1c quy \u01b0\u1edbc \u0111\u1eb7t t\u00ean r\u00f5 r\u00e0ng v\u00e0 nh\u1ea5t qu\u00e1n cho c\u00e1c b\u1ea3ng v\u00e0 c\u1ed9t.<\/p>\n<\/li>\n T\u00e0i li\u1ec7u:<\/strong> Th\u00eam ghi ch\u00fa gi\u1ea3i th\u00edch logic ph\u1ee9c t\u1ea1p ho\u1eb7c c\u00e1c quy t\u1eafc kinh doanh tr\u1ef1c ti\u1ebfp tr\u00ean s\u01a1 \u0111\u1ed3.<\/p>\n<\/li>\n<\/ul>\n Th\u00e0nh th\u1ea1o s\u01a1 \u0111\u1ed3 Th\u1ef1c th\u1ec3 – Quan h\u1ec7 l\u00e0 k\u1ef9 n\u0103ng quan tr\u1ecdng \u0111\u1ed1i v\u1edbi thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u. N\u00f3 t\u1ea1o ra s\u1ef1 k\u1ebft n\u1ed1i gi\u1eefa c\u00e1c y\u00eau c\u1ea7u kinh doanh tr\u1eebu t\u01b0\u1ee3ng v\u00e0 vi\u1ec7c tri\u1ec3n khai k\u1ef9 thu\u1eadt c\u1ee5 th\u1ec3. B\u1eb1ng c\u00e1ch hi\u1ec3u r\u00f5 c\u00e1c th\u1ef1c th\u1ec3, thu\u1ed9c t\u00ednh v\u00e0 m\u1ed1i quan h\u1ec7, b\u1ea1n c\u00f3 th\u1ec3 x\u00e2y d\u1ef1ng c\u00e1c h\u1ec7 th\u1ed1ng c\u00f3 kh\u1ea3 n\u0103ng m\u1edf r\u1ed9ng, d\u1ec5 b\u1ea3o tr\u00ec v\u00e0 hi\u1ec7u qu\u1ea3.<\/p>\n H\u00e3y nh\u1edb r\u1eb1ng s\u1ef1 r\u00f5 r\u00e0ng l\u00e0 m\u1ee5c ti\u00eau. M\u1ed9t s\u01a1 \u0111\u1ed3 c\u1ea7n ph\u1ea3i d\u1ec5 \u0111\u1ecdc \u0111\u1ed1i v\u1edbi b\u1ea5t k\u1ef3 ai tham gia d\u1ef1 \u00e1n. S\u1eed d\u1ee5ng c\u00e1c k\u00fd hi\u1ec7u chu\u1ea9n, tu\u00e2n th\u1ee7 c\u00e1c quy t\u1eafc v\u1ec1 c\u1ea5p \u0111\u1ed9, v\u00e0 lu\u00f4n \u01b0u ti\u00ean t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u. V\u1edbi th\u1ef1c h\u00e0nh th\u01b0\u1eddng xuy\u00ean, vi\u1ec7c t\u1ea1o ra nh\u1eefng h\u01b0\u1edbng d\u1eabn tr\u1ef1c quan n\u00e0y s\u1ebd tr\u1edf th\u00e0nh m\u1ed9t ph\u1ea7n t\u1ef1 nhi\u00ean trong quy tr\u00ecnh l\u00e0m vi\u1ec7c c\u1ee7a b\u1ea1n.<\/p>\n","protected":false},"excerpt":{"rendered":" S\u01a1 \u0111\u1ed3 Th\u1ef1c th\u1ec3 – Quan h\u1ec7, th\u01b0\u1eddng \u0111\u01b0\u1ee3c vi\u1ebft t\u1eaft l\u00e0 ERD, \u0111\u00f3ng vai tr\u00f2 nh\u01b0 b\u1ea3n v\u1ebd thi\u1ebft k\u1ebf cho c\u01a1 s\u1edf d\u1eef li\u1ec7u. N\u00f3 cung c\u1ea5p m\u1ed9t…<\/p>\n","protected":false},"author":1,"featured_media":1686,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_yoast_wpseo_title":"C\u00e1c nguy\u00ean t\u1eafc c\u01a1 b\u1ea3n c\u1ee7a s\u01a1 \u0111\u1ed3 Th\u1ef1c th\u1ec3 - Quan h\u1ec7: H\u01b0\u1edbng d\u1eabn tr\u1ef1c quan cho ng\u01b0\u1eddi m\u1edbi b\u1eaft \u0111\u1ea7u \ud83d\udcca","_yoast_wpseo_metadesc":"H\u1ecdc c\u00e1c ki\u1ebfn th\u1ee9c c\u01a1 b\u1ea3n v\u1ec1 ERD, k\u00fd hi\u1ec7u v\u00e0 c\u1ea5p \u0111\u1ed9. M\u1ed9t h\u01b0\u1edbng d\u1eabn tr\u1ef1c quan \u0111\u1ea7y \u0111\u1ee7 d\u00e0nh cho ng\u01b0\u1eddi m\u1edbi b\u1eaft \u0111\u1ea7u thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u. Kh\u00f4ng c\u1ea7n ph\u1ea7n m\u1ec1m. \ud83d\uddc3\ufe0f","fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[86],"tags":[82,85],"class_list":["post-1685","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-erd","tag-academic","tag-erd"],"yoast_head":"\nC\u00e1c th\u00e0nh ph\u1ea7n c\u1ed1t l\u00f5i c\u1ee7a ERD \ud83d\udd27<\/h2>\n
1. Th\u1ef1c th\u1ec3 \ud83c\udfe2<\/h3>\n
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2. Thu\u1ed9c t\u00ednh \ud83c\udff7\ufe0f<\/h3>\n
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3. M\u1ed1i quan h\u1ec7 \ud83d\udd17<\/h3>\n
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Cardinality v\u00e0 T\u00ednh b\u1eaft bu\u1ed9c \ud83d\udccf<\/h2>\n
C\u00e1c lo\u1ea1i Cardinality<\/h3>\n
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\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n Hi\u1ec3u v\u1ec1 T\u00ednh b\u1eaft bu\u1ed9c<\/h3>\n
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Phong c\u00e1ch k\u00fd hi\u1ec7u \ud83c\udfa8<\/h2>\n
K\u00fd hi\u1ec7u Chen<\/h3>\n
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K\u00fd hi\u1ec7u Ch\u00e2n chim<\/h3>\n
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S\u01a1 \u0111\u1ed3 l\u1edbp UML<\/h3>\n
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\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n Thi\u1ebft k\u1ebf l\u01b0\u1ee3c \u0111\u1ed3 c\u01a1 s\u1edf d\u1eef li\u1ec7u \ud83d\udee0\ufe0f<\/h2>\n
B\u01b0\u1edbc 1: X\u00e1c \u0111\u1ecbnh c\u00e1c th\u1ef1c th\u1ec3<\/h3>\n
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B\u01b0\u1edbc 2: X\u00e1c \u0111\u1ecbnh thu\u1ed9c t\u00ednh<\/h3>\n
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B\u01b0\u1edbc 3: X\u00e1c \u0111\u1ecbnh m\u1ed1i quan h\u1ec7<\/h3>\n
B\u01b0\u1edbc 4: X\u00e1c \u0111\u1ecbnh t\u00ednh cardinality<\/h3>\n
B\u01b0\u1edbc 5: Chu\u1ea9n h\u00f3a d\u1eef li\u1ec7u<\/h3>\n
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Nh\u1eefng sai l\u1ea7m ph\u1ed5 bi\u1ebfn c\u1ea7n tr\u00e1nh \u26a0\ufe0f<\/h2>\n
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V\u00ed d\u1ee5: Gi\u1ea3i quy\u1ebft m\u1ed1i quan h\u1ec7 nhi\u1ec1u-\u0111a<\/h3>\n
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C\u00e1c th\u1ef1c h\u00e0nh t\u1ed1t nh\u1ea5t cho b\u1ea3o tr\u00ec \ud83d\udcdd<\/h2>\n
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K\u1ebft lu\u1eadn \ud83c\udfc1<\/h2>\n