{"id":477314,"date":"2023-08-09T09:11:08","date_gmt":"2023-08-09T09:11:08","guid":{"rendered":""},"modified":"2023-09-05T11:14:30","modified_gmt":"2023-09-05T11:14:30","slug":"functional-dependency","status":"publish","type":"wiki","link":"https:\/\/oneproxy.pro\/vn\/wiki\/functional-dependency\/","title":{"rendered":"S\u1ef1 ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng"},"content":{"rendered":"

S\u1ef1 ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng l\u00e0 nguy\u00ean t\u1eafc c\u1ed1t l\u00f5i trong l\u0129nh v\u1ef1c chu\u1ea9n h\u00f3a c\u01a1 s\u1edf d\u1eef li\u1ec7u, do \u0111\u00f3, l\u00e0 m\u1ed9t ph\u1ea7n c\u01a1 b\u1ea3n c\u1ee7a thi\u1ebft k\u1ebf v\u00e0 qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u. N\u00f3 ph\u1ee5c v\u1ee5 \u0111\u1ec3 lo\u1ea1i b\u1ecf s\u1ef1 d\u01b0 th\u1eeba v\u00e0 ng\u0103n ch\u1eb7n s\u1ef1 kh\u00f4ng nh\u1ea5t qu\u00e1n c\u00f3 th\u1ec3 x\u1ea3y ra, do \u0111\u00f3 l\u00e0m t\u0103ng hi\u1ec7u qu\u1ea3 c\u1ee7a h\u1ec7 th\u1ed1ng qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/p>\n

Ngu\u1ed3n g\u1ed1c c\u1ee7a s\u1ef1 ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng: T\u1ed5ng quan l\u1ecbch s\u1eed<\/h2>\n

Kh\u00e1i ni\u1ec7m v\u1ec1 s\u1ef1 ph\u1ee5 thu\u1ed9c h\u00e0m b\u1eaft ngu\u1ed3n t\u1eeb l\u0129nh v\u1ef1c l\u00fd thuy\u1ebft c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7. N\u00f3 \u0111\u01b0\u1ee3c Edgar F. Codd gi\u1edbi thi\u1ec7u l\u1ea7n \u0111\u1ea7u ti\u00ean v\u00e0o n\u0103m 1970 nh\u01b0 m\u1ed9t ph\u1ea7n trong c\u00f4ng tr\u00ecnh mang t\u00ednh \u0111\u1ed9t ph\u00e1 c\u1ee7a \u00f4ng v\u1ec1 m\u00f4 h\u00ecnh quan h\u1ec7 \u0111\u1ec3 qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u. Codd, m\u1ed9t nh\u00e0 khoa h\u1ecdc m\u00e1y t\u00ednh t\u1ea1i IBM, c\u0169ng \u0111\u01b0\u1ee3c c\u00f4ng nh\u1eadn v\u00ec nh\u1eefng \u0111\u00f3ng g\u00f3p \u0111\u00e1ng k\u1ec3 c\u1ee7a \u00f4ng trong vi\u1ec7c ph\u00e1t tri\u1ec3n Ng\u00f4n ng\u1eef truy v\u1ea5n c\u00f3 c\u1ea5u tr\u00fac (SQL), ng\u00f4n ng\u1eef ti\u00eau chu\u1ea9n cho c\u00e1c h\u1ec7 th\u1ed1ng qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7.<\/p>\n

M\u1ed9t c\u00e1i nh\u00ecn s\u00e2u s\u1eafc v\u1ec1 s\u1ef1 ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng<\/h2>\n

S\u1ef1 ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng l\u00e0 m\u1ed9t thu\u1ed9c t\u00ednh c\u1ee7a t\u1eadp thu\u1ed9c t\u00ednh c\u1ee7a c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7. N\u00f3i m\u1ed9t c\u00e1ch \u0111\u01a1n gi\u1ea3n, m\u1ed9t t\u1eadp h\u1ee3p c\u00e1c thu\u1ed9c t\u00ednh A s\u1ebd x\u00e1c \u0111\u1ecbnh m\u1ed9t c\u00e1ch c\u00f3 ch\u1ee9c n\u0103ng m\u1ed9t t\u1eadp h\u1ee3p c\u00e1c thu\u1ed9c t\u00ednh B n\u1ebfu, \u0111\u1ed1i v\u1edbi m\u1ecdi phi\u00ean b\u1ea3n h\u1ee3p l\u1ec7 c\u1ee7a c\u01a1 s\u1edf d\u1eef li\u1ec7u, t\u1ea5t c\u1ea3 c\u00e1c b\u1ed9 d\u1eef li\u1ec7u c\u00f3 c\u00f9ng gi\u00e1 tr\u1ecb A c\u0169ng c\u00f3 c\u00f9ng gi\u00e1 tr\u1ecb B. N\u00f3i c\u00e1ch kh\u00e1c, n\u1ebfu thu\u1ed9c t\u00ednh B ph\u1ee5 thu\u1ed9c h\u00e0m v\u00e0o thu\u1ed9c t\u00ednh A th\u00ec v\u1edbi m\u1ed7i gi\u00e1 tr\u1ecb c\u1ee7a A s\u1ebd c\u00f3 ch\u00ednh x\u00e1c m\u1ed9t gi\u00e1 tr\u1ecb c\u1ee7a B.<\/p>\n

Kh\u00e1i ni\u1ec7m n\u00e0y \u0111\u00f3ng m\u1ed9t vai tr\u00f2 quan tr\u1ecdng trong qu\u00e1 tr\u00ecnh chu\u1ea9n h\u00f3a c\u01a1 s\u1edf d\u1eef li\u1ec7u, gi\u00fap gi\u1ea3m s\u1ef1 d\u01b0 th\u1eeba d\u1eef li\u1ec7u v\u00e0 c\u1ea3i thi\u1ec7n t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u. B\u1eb1ng c\u00e1ch x\u00e1c \u0111\u1ecbnh c\u00e1c ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng, ng\u01b0\u1eddi ta c\u00f3 th\u1ec3 quy\u1ebft \u0111\u1ecbnh c\u00e1ch chia c\u01a1 s\u1edf d\u1eef li\u1ec7u th\u00e0nh nhi\u1ec1u b\u1ea3ng t\u1ed1t nh\u1ea5t m\u00e0 kh\u00f4ng l\u00e0m m\u1ea5t b\u1ea5t k\u1ef3 th\u00f4ng tin n\u00e0o, t\u1eeb \u0111\u00f3 t\u1ea1o ra c\u1ea5u tr\u00fac c\u01a1 s\u1edf d\u1eef li\u1ec7u m\u1ea1ch l\u1ea1c v\u00e0 hi\u1ec7u qu\u1ea3 h\u01a1n.<\/p>\n

S\u1ef1 ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng: H\u1eadu tr\u01b0\u1eddng<\/h2>\n

S\u1ef1 ph\u1ee5 thu\u1ed9c h\u00e0m \u0111\u01b0\u1ee3c \u0111i\u1ec1u ch\u1ec9nh b\u1edfi m\u1ed9t t\u1eadp h\u1ee3p c\u00e1c ti\u00ean \u0111\u1ec1 \u0111\u01b0\u1ee3c g\u1ecdi l\u00e0 Ti\u00ean \u0111\u1ec1 Armstrong. Nh\u1eefng ti\u00ean \u0111\u1ec1 n\u00e0y, bao g\u1ed3m t\u00ednh ph\u1ea3n x\u1ea1, t\u00ednh t\u0103ng c\u01b0\u1eddng v\u00e0 t\u00ednh b\u1eafc c\u1ea7u, l\u00e0 c\u00e1c quy t\u1eafc \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 suy ra t\u1ea5t c\u1ea3 c\u00e1c ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng tr\u00ean c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7.<\/p>\n

V\u00ed d\u1ee5: ti\u00ean \u0111\u1ec1 ph\u1ea3n x\u1ea1 ph\u00e1t bi\u1ec3u r\u1eb1ng n\u1ebfu m\u1ed9t t\u1eadp thu\u1ed9c t\u00ednh B l\u00e0 t\u1eadp con c\u1ee7a t\u1eadp thu\u1ed9c t\u00ednh A th\u00ec A s\u1ebd x\u00e1c \u0111\u1ecbnh B v\u1ec1 m\u1eb7t h\u00e0m s\u1ed1. T\u01b0\u01a1ng t\u1ef1, ti\u00ean \u0111\u1ec1 t\u0103ng c\u01b0\u1eddng cho bi\u1ebft r\u1eb1ng n\u1ebfu A x\u00e1c \u0111\u1ecbnh B th\u00ec A, c\u00f9ng v\u1edbi b\u1ea5t k\u1ef3 thu\u1ed9c t\u00ednh b\u1ed5 sung n\u00e0o C, x\u00e1c \u0111\u1ecbnh B. Cu\u1ed1i c\u00f9ng, quy t\u1eafc b\u1eafc c\u1ea7u ph\u00e1t bi\u1ec3u r\u1eb1ng n\u1ebfu A x\u00e1c \u0111\u1ecbnh B v\u00e0 B x\u00e1c \u0111\u1ecbnh C th\u00ec A x\u00e1c \u0111\u1ecbnh C.<\/p>\n

C\u00e1c t\u00ednh n\u0103ng ch\u00ednh c\u1ee7a ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng<\/h2>\n

S\u1ef1 ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng \u0111\u01b0\u1ee3c \u0111\u1eb7c tr\u01b0ng b\u1edfi m\u1ed9t s\u1ed1 t\u00ednh n\u0103ng ch\u00ednh:<\/p>\n

    \n
  1. T\u00ednh duy nh\u1ea5t: N\u1ebfu m\u1ed9t t\u1eadp h\u1ee3p c\u00e1c thu\u1ed9c t\u00ednh A x\u00e1c \u0111\u1ecbnh ch\u1ee9c n\u0103ng B th\u00ec s\u1ebd c\u00f3 m\u1ed9t gi\u00e1 tr\u1ecb B duy nh\u1ea5t cho m\u1ed7i gi\u00e1 tr\u1ecb A.<\/li>\n
  2. Suy lu\u1eadn: C\u00e1c ph\u1ee5 thu\u1ed9c h\u00e0m c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c suy ra t\u1eeb m\u1ed9t t\u1eadp h\u1ee3p c\u00e1c ph\u1ee5 thu\u1ed9c nh\u1ea5t \u0111\u1ecbnh b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng c\u00e1c ti\u00ean \u0111\u1ec1 Armstrong.<\/li>\n
  3. B\u1ea3o to\u00e0n ph\u1ea7n ph\u1ee5 thu\u1ed9c: C\u00e1c ph\u1ea7n ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng c\u00f3 th\u1ec3 gi\u00fap b\u1ea3o to\u00e0n c\u00e1c ph\u1ea7n ph\u1ee5 thu\u1ed9c khi c\u01a1 s\u1edf d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c ph\u00e2n t\u00e1ch th\u00e0nh nhi\u1ec1u b\u1ea3ng.<\/li>\n
  4. K\u1ebft n\u1ed1i kh\u00f4ng m\u1ea5t d\u1eef li\u1ec7u: Vi\u1ec7c s\u1eed d\u1ee5ng h\u1ee3p l\u00fd c\u00e1c ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng c\u00f3 th\u1ec3 \u0111\u1ea3m b\u1ea3o thu\u1ed9c t\u00ednh k\u1ebft n\u1ed1i kh\u00f4ng m\u1ea5t d\u1eef li\u1ec7u, \u0111\u1ea3m b\u1ea3o r\u1eb1ng kh\u00f4ng c\u00f3 th\u00f4ng tin n\u00e0o b\u1ecb m\u1ea5t khi ph\u00e2n t\u00e1ch c\u01a1 s\u1edf d\u1eef li\u1ec7u th\u00e0nh c\u00e1c b\u1ea3ng v\u00e0 sau \u0111\u00f3 k\u1ebft h\u1ee3p l\u1ea1i.<\/li>\n<\/ol>\n

    Ph\u00e2n lo\u1ea1i ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng<\/h2>\n

    S\u1ef1 ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c ph\u00e2n lo\u1ea1i th\u00e0nh nhi\u1ec1u lo\u1ea1i kh\u00e1c nhau:<\/p>\n\n\n\n\n\n\n\n\n
    Ki\u1ec3u<\/th>\nS\u1ef1 mi\u00eau t\u1ea3<\/th>\n<\/tr>\n<\/thead>\n
    S\u1ef1 ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng t\u1ea7m th\u01b0\u1eddng<\/td>\nS\u1ef1 ph\u1ee5 thu\u1ed9c c\u1ee7a m\u1ed9t thu\u1ed9c t\u00ednh v\u00e0o si\u00eau t\u1eadp h\u1ee3p c\u1ee7a ch\u00ednh n\u00f3.<\/td>\n<\/tr>\n
    S\u1ef1 ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng kh\u00f4ng t\u1ea7m th\u01b0\u1eddng<\/td>\nS\u1ef1 ph\u1ee5 thu\u1ed9c c\u1ee7a m\u1ed9t thu\u1ed9c t\u00ednh v\u00e0o m\u1ed9t t\u1eadp h\u1ee3p kh\u00f4ng bao g\u1ed3m n\u00f3.<\/td>\n<\/tr>\n
    S\u1ef1 ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng ho\u00e0n to\u00e0n kh\u00f4ng t\u1ea7m th\u01b0\u1eddng<\/td>\nM\u1ed9t s\u1ef1 ph\u1ee5 thu\u1ed9c trong \u0111\u00f3 b\u00ean tr\u00e1i v\u00e0 b\u00ean ph\u1ea3i r\u1eddi r\u1ea1c.<\/td>\n<\/tr>\n
    S\u1ef1 ph\u1ee5 thu\u1ed9c b\u1eafc c\u1ea7u<\/td>\nM\u1ed9t d\u1ea1ng ph\u1ee5 thu\u1ed9c h\u00e0m trong \u0111\u00f3 n\u1ebfu A \u2192 B v\u00e0 B \u2192 C th\u00ec A \u2192 C.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    S\u1eed d\u1ee5ng th\u1ef1c t\u1ebf, v\u1ea5n \u0111\u1ec1 v\u00e0 gi\u1ea3i ph\u00e1p<\/h2>\n

    C\u00e1c ph\u1ea7n ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng r\u1ea5t quan tr\u1ecdng trong qu\u00e1 tr\u00ecnh chu\u1ea9n h\u00f3a c\u01a1 s\u1edf d\u1eef li\u1ec7u, trong \u0111\u00f3 ch\u00fang \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 lo\u1ea1i b\u1ecf s\u1ef1 d\u01b0 th\u1eeba v\u00e0 c\u1ea3i thi\u1ec7n t\u00ednh nh\u1ea5t qu\u00e1n c\u1ee7a d\u1eef li\u1ec7u. Tuy nhi\u00ean, vi\u1ec7c suy ra c\u00e1c ph\u1ee5 thu\u1ed9c h\u00e0m t\u1eeb m\u1ed9t t\u1eadp d\u1eef li\u1ec7u l\u1edbn c\u00f3 th\u1ec3 t\u1ed1n k\u00e9m v\u1ec1 m\u1eb7t t\u00ednh to\u00e1n v\u00e0 t\u1ed1n th\u1eddi gian. M\u1ed9t trong nh\u1eefng chi\u1ebfn l\u01b0\u1ee3c \u0111\u1ec3 gi\u1ea3m thi\u1ec3u \u0111i\u1ec1u n\u00e0y l\u00e0 s\u1eed d\u1ee5ng thu\u1eadt to\u00e1n suy lu\u1eadn ph\u1ee5 thu\u1ed9c, thu\u1eadt to\u00e1n n\u00e0y c\u00f3 th\u1ec3 r\u00fat ra m\u1ee9c che ph\u1ee7 t\u1ed1i thi\u1ec3u m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3 cho t\u1eadp h\u1ee3p c\u00e1c ph\u1ee5 thu\u1ed9c.<\/p>\n

    So s\u00e1nh v\u1edbi c\u00e1c \u0111i\u1ec1u kho\u1ea3n li\u00ean quan<\/h2>\n\n\n\n\n\n\n\n
    Thu\u1eadt ng\u1eef<\/th>\nS\u1ef1 mi\u00eau t\u1ea3<\/th>\n<\/tr>\n<\/thead>\n
    Ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng<\/td>\nM\u1ed9t m\u1ed1i quan h\u1ec7 duy nh\u1ea5t gi\u1eefa c\u00e1c thu\u1ed9c t\u00ednh c\u1ee7a c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7.<\/td>\n<\/tr>\n
    S\u1ef1 ph\u1ee5 thu\u1ed9c \u0111a gi\u00e1 tr\u1ecb<\/td>\nR\u00e0ng bu\u1ed9c \u0111\u1ea7y \u0111\u1ee7 gi\u1eefa hai b\u1ed9 thu\u1ed9c t\u00ednh trong m\u1ed9t quan h\u1ec7.<\/td>\n<\/tr>\n
    Tham gia ph\u1ee5 thu\u1ed9c<\/td>\nM\u1ed9t r\u00e0ng bu\u1ed9c v\u1ec1 vi\u1ec7c ph\u00e2n r\u00e3 m\u1ed9t quan h\u1ec7 c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    Quan \u0111i\u1ec3m t\u01b0\u01a1ng lai v\u00e0 c\u00f4ng ngh\u1ec7 m\u1edbi n\u1ed5i<\/h2>\n

    Khi kh\u1ed1i l\u01b0\u1ee3ng d\u1eef li\u1ec7u ti\u1ebfp t\u1ee5c t\u0103ng, hi\u1ec7u su\u1ea5t v\u00e0 hi\u1ec7u qu\u1ea3 c\u1ee7a vi\u1ec7c qu\u1ea3n l\u00fd d\u1eef li\u1ec7u n\u00e0y s\u1ebd ph\u1ee5 thu\u1ed9c v\u00e0o s\u1ef1 ph\u00e1t tri\u1ec3n c\u1ee7a c\u00e1c nguy\u00ean t\u1eafc qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u nh\u01b0 c\u00e1c ph\u1ea7n ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng. C\u00e1c thu\u1eadt to\u00e1n h\u1ecdc m\u00e1y \u0111\u1ec3 suy ra s\u1ef1 ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng t\u1eeb d\u1eef li\u1ec7u c\u00f3 th\u1ec3 gi\u00fap c\u1ea3i thi\u1ec7n hi\u1ec7u su\u1ea5t v\u00e0 kh\u1ea3 n\u0103ng m\u1edf r\u1ed9ng c\u1ee7a h\u1ec7 th\u1ed1ng qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/p>\n

    S\u1ef1 giao nhau c\u1ee7a m\u00e1y ch\u1ee7 proxy v\u00e0 c\u00e1c ph\u1ea7n ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng<\/h2>\n

    M\u1eb7c d\u00f9 c\u00e1c ph\u1ea7n ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng ch\u1ee7 y\u1ebfu li\u00ean quan \u0111\u1ebfn b\u1ed1i c\u1ea3nh qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u nh\u01b0ng v\u1eabn c\u00f3 m\u1ed1i quan h\u1ec7 ti\u1ebfp tuy\u1ebfn v\u1edbi l\u0129nh v\u1ef1c m\u00e1y ch\u1ee7 proxy. C\u1ee5 th\u1ec3, m\u00e1y ch\u1ee7 proxy th\u01b0\u1eddng s\u1eed d\u1ee5ng c\u01a1 s\u1edf d\u1eef li\u1ec7u \u0111\u1ec3 qu\u1ea3n l\u00fd d\u1eef li\u1ec7u ng\u01b0\u1eddi d\u00f9ng, ki\u1ec3m so\u00e1t truy c\u1eadp v\u00e0 nh\u1eadt k\u00fd y\u00eau c\u1ea7u. B\u1eb1ng c\u00e1ch \u00e1p d\u1ee5ng c\u00e1c nguy\u00ean t\u1eafc ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng, c\u00e1c nh\u00e0 cung c\u1ea5p d\u1ecbch v\u1ee5 proxy nh\u01b0 OneProxy c\u00f3 th\u1ec3 t\u1ed1i \u01b0u h\u00f3a c\u1ea5u tr\u00fac c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a h\u1ecd \u0111\u1ec3 c\u1ea3i thi\u1ec7n hi\u1ec7u su\u1ea5t v\u00e0 t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u.<\/p>\n

    Li\u00ean k\u1ebft li\u00ean quan<\/h2>\n

    \u0110\u1ec3 bi\u1ebft th\u00eam th\u00f4ng tin v\u1ec1 c\u00e1c ph\u1ea7n ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng, b\u1ea1n c\u00f3 th\u1ec3 tham kh\u1ea3o c\u00e1c t\u00e0i nguy\u00ean sau:<\/p>\n

      \n
    1. Kh\u00e1i ni\u1ec7m h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a Silberschatz, Korth v\u00e0 Sudarshan<\/a><\/li>\n
    2. C\u00e1c ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng trong DBMS \u2013 GeeksforGeeks<\/a><\/li>\n
    3. Gi\u1edbi thi\u1ec7u v\u1ec1 h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a CJ Date<\/a><\/li>\n
    4. Nguy\u00ean t\u1eafc c\u01a1 b\u1ea3n c\u1ee7a h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a Ramez Elmasri v\u00e0 Shamkant B. Navathe<\/a><\/li>\n<\/ol>\n

      H\u00e3y nh\u1edb r\u1eb1ng, vi\u1ec7c hi\u1ec3u v\u00e0 \u00e1p d\u1ee5ng \u0111\u00fang c\u00e1ch c\u00e1c ph\u1ea7n ph\u1ee5 thu\u1ed9c ch\u1ee9c n\u0103ng c\u00f3 th\u1ec3 mang l\u1ea1i h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u hi\u1ec7u qu\u1ea3, \u0111\u00e1ng tin c\u1eady v\u00e0 c\u00f3 th\u1ec3 m\u1edf r\u1ed9ng.<\/p>","protected":false},"featured_media":477315,"menu_order":0,"template":"","meta":{"_acf_changed":false,"content-type":"","inline_featured_image":false,"footnotes":""},"class_list":["post-477314","wiki","type-wiki","status-publish","has-post-thumbnail","hentry"],"acf":{"faq_title":"Frequently Asked Questions about Functional Dependency: A Fundamental Concept in Database Theory<\/mark>","faq_items":[{"question":"What is Functional Dependency?","answer":"

      Functional dependency is a core principle in the field of database normalization. It serves to eliminate redundancy and prevent possible inconsistency, thereby increasing the efficiency of database management systems.<\/p>"},{"question":"Who introduced the concept of Functional Dependency?","answer":"

      The concept of functional dependency was first introduced by Edgar F. Codd in 1970 as part of his groundbreaking work on the relational model for database management.<\/p>"},{"question":"How does Functional Dependency work in a relational database?","answer":"

      In a relational database, a set of attributes A functionally determines a set of attributes B if, for every valid instance of the database, all tuples with the same A-value also have the same B-value.<\/p>"},{"question":"What are Armstrong's Axioms?","answer":"

      Armstrong's Axioms are a set of rules that govern functional dependency. They include reflexivity, augmentation, and transitivity. These axioms are used to infer all the functional dependencies on a relational database.<\/p>"},{"question":"What are the key features of Functional Dependencies?","answer":"

      Functional dependencies have several key features: Uniqueness, Inference, Dependency preservation, and Lossless join.<\/p>"},{"question":"What are the different types of Functional Dependencies?","answer":"

      Functional dependencies can be categorized into various types: Trivial, Non-trivial, Completely non-trivial, and Transitive Dependency.<\/p>"},{"question":"What are the practical uses of Functional Dependencies?","answer":"

      Functional dependencies are used in database normalization, where they eliminate redundancy and improve data consistency. They help in preserving dependencies when a database is decomposed into multiple tables.<\/p>"},{"question":"What are the challenges related to Functional Dependencies?","answer":"

      Inferring functional dependencies from a large dataset can be computationally expensive and time-consuming. These problems can be mitigated by using a dependency inference algorithm.<\/p>"},{"question":"How are Functional Dependencies relevant to the future of database technologies?","answer":"

      As data volumes continue to grow, principles like functional dependencies will be crucial for the efficient management of this data. Machine learning algorithms for inferring functional dependencies from data can improve the performance and scalability of database management systems.<\/p>"},{"question":"How are Functional Dependencies related to Proxy Servers?","answer":"

      Functional dependencies can indirectly influence the functioning of proxy servers. Proxy servers often use databases to manage user data, access controls, and request logs. Therefore, optimizing database structures using functional dependencies can enhance the performance and data integrity of proxy services like OneProxy.<\/p>"}]},"_links":{"self":[{"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/wiki\/477314","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/wiki"}],"about":[{"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/types\/wiki"}],"version-history":[{"count":0,"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/wiki\/477314\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/media\/477315"}],"wp:attachment":[{"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/media?parent=477314"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}