{"id":49973,"date":"2023-12-17T05:29:51","date_gmt":"2023-12-17T05:29:51","guid":{"rendered":"https:\/\/masterskills.org\/blog\/top-20-cau-hoi-phong-van-backend-thuong-gap.html"},"modified":"2023-12-17T05:29:51","modified_gmt":"2023-12-17T05:29:51","slug":"top-20-cau-hoi-phong-van-backend-thuong-gap","status":"publish","type":"post","link":"https:\/\/masterskills.org\/blog\/top-20-cau-hoi-phong-van-backend-thuong-gap.html","title":{"rendered":"Top 20 C\u00e2u H\u1ecfi Ph\u1ecfng V\u1ea5n Backend Th\u01b0\u1eddng G\u1eb7p\u00a0"},"content":{"rendered":"
\n

Backend l\u00e0 x\u01b0\u01a1ng s\u1ed1ng c\u1ee7a c\u00e1c \u1ee9ng d\u1ee5ng web, x\u1eed l\u00fd x\u1eed l\u00fd d\u1eef li\u1ec7u, logic ph\u00eda m\u00e1y ch\u1ee7 v\u00e0 qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u. \u0110\u1ec3 v\u01b0\u1ee3t qua c\u00e1c cu\u1ed9c ph\u1ecfng v\u1ea5n Backend kh\u00f3 nh\u1eb1n, b\u1ea1n ph\u1ea3i c\u00f3 hi\u1ec3u bi\u1ebft v\u1eefng ch\u1eafc v\u1ec1 c\u00e1c kh\u00e1i ni\u1ec7m v\u00e0 nguy\u00ean t\u1eafc c\u01a1 b\u1ea3n trong l\u0129nh v\u1ef1c n\u00e0y. Trong b\u00e0i vi\u1ebft d\u01b0\u1edbi \u0111\u00e2y, Masterskills s\u1ebd c\u00f9ng b\u1ea1n \u0111i qua 20 c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n Backend<\/strong> th\u01b0\u1eddng g\u1eb7p nh\u1ea5t, gi\u00fap b\u1ea1n c\u00f3 \u0111\u01b0\u1ee3c c\u00e1i nh\u00ecn t\u1ed5ng qu\u00e1t v\u1ec1 nh\u1eefng ki\u1ebfn th\u1ee9c tr\u1ecdng t\u00e2m hay \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng!<\/p>\n

C\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n Backend c\u01a1 b\u1ea3n\u00a0<\/strong><\/h2>\n

\u0110\u1ea7u ti\u00ean, h\u00e3y c\u00f9ng Masterskills s\u01a1 l\u01b0\u1ee3c v\u1ec1 m\u1ed9t s\u1ed1 c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n Backend<\/strong> c\u01a1 b\u1ea3n. \u0110\u00e2y l\u00e0 c\u00e1c c\u00e2u h\u1ecfi th\u01b0\u1eddng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u1edf \u0111\u1ea7u bu\u1ed5i ph\u1ecfng v\u1ea5n nh\u1eb1m \u201cl\u00e0m n\u00f3ng\u201d v\u00e0 t\u1ea1o ti\u1ec1n \u0111\u1ec1 cho c\u00e1c c\u00e2u h\u1ecfi k\u1ef9 thu\u1eadt \u1edf ph\u1ea7n sau.<\/p>\n

1. N\u00eau m\u1ee5c \u0111\u00edch c\u1ee7a back-end l\u00e0 g\u00ec?\u00a0<\/strong><\/h3>\n

Trong ph\u00e1t tri\u1ec3n ph\u1ea7n m\u1ec1m, back-end l\u00e0 m\u1ed9t ph\u1ea7n quan tr\u1ecdng c\u1ee7a h\u1ec7 th\u1ed1ng, ch\u1ecbu tr\u00e1ch nhi\u1ec7m x\u1eed l\u00fd c\u00e1c quy tr\u00ecnh x\u1eed l\u00fd d\u1eef li\u1ec7u v\u00e0 logic m\u00e0 ng\u01b0\u1eddi d\u00f9ng kh\u00f4ng nh\u00ecn th\u1ea5y tr\u1ef1c ti\u1ebfp. M\u1ee5c \u0111\u00edch ch\u00ednh c\u1ee7a back-end l\u00e0 x\u00e2y d\u1ef1ng c\u00e1c h\u1ec7 th\u1ed1ng v\u00e0 quy tr\u00ecnh \u0111\u1ec3 x\u1eed l\u00fd, l\u01b0u tr\u1eef v\u00e0 truy xu\u1ea5t d\u1eef li\u1ec7u, \u0111\u1ea3m b\u1ea3o h\u1ec7 th\u1ed1ng ho\u1ea1t \u0111\u1ed9ng m\u1ed9t c\u00e1ch \u1ed5n \u0111\u1ecbnh v\u00e0 duy tr\u00ec t\u00ednh b\u1ea3o m\u1eadt.<\/p>\n

2. Quy tr\u00ecnh \u0111i\u1ec3n h\u00ecnh \u0111\u1ec3 tri\u1ec3n khai m\u1ed9t t\u00ednh n\u0103ng m\u1edbi trong backend l\u00e0 g\u00ec?\u00a0<\/strong><\/h3>\n

Quy tr\u00ecnh tri\u1ec3n khai c\u00e1c t\u00ednh n\u0103ng tr\u00ean back-end c\u00f3 th\u1ec3 kh\u00e1c nhau t\u00f9y thu\u1ed9c v\u00e0o c\u00f4ng ty v\u00e0 nh\u00f3m c\u00f4ng ngh\u1ec7. Tuy nhi\u00ean, quy tr\u00ecnh l\u00e0m vi\u1ec7c \u0111i\u1ec3n h\u00ecnh s\u1ebd bao g\u1ed3m vi\u1ec7c th\u1ea3o lu\u1eadn v\u1ec1 t\u00ednh n\u0103ng v\u1edbi c\u00e1c b\u00ean li\u00ean quan, thi\u1ebft k\u1ebf v\u00e0 t\u1ea1o nguy\u00ean m\u1eabu t\u00ednh n\u0103ng, vi\u1ebft m\u00e3 v\u00e0 th\u1ef1c hi\u1ec7n QA th\u1eed nghi\u1ec7m.\u00a0<\/p>\n

Trong h\u1ea7u h\u1ebft c\u00e1c tr\u01b0\u1eddng h\u1ee3p, back-end developer s\u1ebd l\u00e0m vi\u1ec7c v\u1edbi nh\u00e0 ph\u00e1t tri\u1ec3n giao di\u1ec7n ng\u01b0\u1eddi d\u00f9ng \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o r\u1eb1ng d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c truy\u1ec1n ch\u00ednh x\u00e1c gi\u1eefa m\u00e1y kh\u00e1ch v\u00e0 m\u00e1y ch\u1ee7. \u0110i\u1ec1u c\u1ea7n thi\u1ebft l\u00e0 \u0111\u1ea3m b\u1ea3o r\u1eb1ng m\u1ecdi t\u00ednh n\u0103ng m\u1edbi \u0111\u1ec1u t\u01b0\u01a1ng th\u00edch ng\u01b0\u1ee3c v\u1edbi c\u00e1c phi\u00ean b\u1ea3n tr\u01b0\u1edbc c\u1ee7a \u1ee9ng d\u1ee5ng.<\/p>\n

3. Gi\u1ea3i th\u00edch nguy\u00ean t\u1eafc c\u1ee7a nguy\u00ean t\u1eafc DRY v\u00e0 DIE\u00a0<\/strong><\/h3>\n

Nguy\u00ean t\u1eafc DRY (Don\u2019t Repeat Yourself) l\u00e0 m\u1ed9t nguy\u00ean t\u1eafc ph\u00e1t tri\u1ec3n ph\u1ea7n m\u1ec1m quy \u0111\u1ecbnh r\u1eb1ng c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n kh\u00f4ng n\u00ean sao ch\u00e9p m\u00e3. M\u00e3 tr\u00f9ng l\u1eb7p c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn c\u00e1c v\u1ea5n \u0111\u1ec1 v\u1ec1 b\u1ea3o tr\u00ec v\u00ec c\u00e1c thay \u0111\u1ed5i c\u1ea7n \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n \u1edf nhi\u1ec1u n\u01a1i.\u00a0<\/p>\n

Nguy\u00ean t\u1eafc DIE (Duplication Is Evil) c\u0169ng kh\u00e1 t\u01b0\u01a1ng t\u1ef1 v\u1edbi nguy\u00ean t\u1eafc DRY. Tuy nhi\u00ean, n\u00f3 ti\u1ebfn th\u00eam m\u1ed9t b\u01b0\u1edbc b\u1eb1ng c\u00e1ch tuy\u00ean b\u1ed1 r\u1eb1ng ngay c\u1ea3 m\u1ed9t l\u01b0\u1ee3ng nh\u1ecf tr\u00f9ng l\u1eb7p c\u0169ng kh\u00f4ng \u0111\u01b0\u1ee3c ch\u1ea5p nh\u1eadn.<\/p>\n

4. M\u1ed9t web server l\u00e0 g\u00ec?\u00a0<\/strong><\/h3>\n

M\u00e1y web server l\u00e0 m\u1ed9t m\u00e1y t\u00ednh l\u01b0u tr\u1eef v\u00e0 cung c\u1ea5p c\u00e1c trang web. Khi b\u1ea1n nh\u1eadp m\u1ed9t URL v\u00e0o tr\u00ecnh duy\u1ec7t c\u1ee7a m\u00ecnh, tr\u00ecnh duy\u1ec7t s\u1ebd li\u00ean l\u1ea1c v\u1edbi web server v\u00e0 y\u00eau c\u1ea7u trang. Sau \u0111\u00f3, web server s\u1ebd g\u1eedi trang tr\u1edf l\u1ea1i tr\u00ecnh duy\u1ec7t, tr\u00ecnh duy\u1ec7t n\u00e0y s\u1ebd hi\u1ec3n th\u1ecb n\u00f3 tr\u00ean m\u00e0n h\u00ecnh c\u1ee7a b\u1ea1n. Apache v\u00e0 NGINX l\u00e0 m\u1ed9t s\u1ed1 m\u00e1y ch\u1ee7 web ph\u1ed5 bi\u1ebfn nh\u1ea5t \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng b\u1edfi c\u00e1c \u1ee9ng d\u1ee5ng ph\u1ee5 tr\u1ee3. Web server c\u0169ng c\u00f3 th\u1ec3 l\u01b0u tr\u1eef c\u00e1c t\u00e0i nguy\u00ean kh\u00e1c, nh\u01b0 h\u00ecnh \u1ea3nh ho\u1eb7c video.<\/p>\n

5. H\u00e3y n\u00f3i v\u1ec1 tr\u1ea3i nghi\u1ec7m c\u1ee7a b\u1ea1n khi l\u00e0m vi\u1ec7c trong m\u1ed9t nh\u00f3m<\/strong><\/h3>\n

Th\u00f4ng th\u01b0\u1eddng, c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n back-end \u0111\u01b0\u1ee3c y\u00eau c\u1ea7u l\u00e0m vi\u1ec7c theo nh\u00f3m. Khi tr\u1ea3 l\u1eddi c\u00e2u h\u1ecfi n\u00e0y, \u1ee9ng vi\u00ean c\u00f3 th\u1ec3 \u0111\u01b0a ra m\u1ed9t v\u00e0i v\u00ed d\u1ee5 v\u1ec1 nh\u1eefng l\u1ea7n h\u1ecd l\u00e0m vi\u1ec7c nh\u00f3m.<\/p>\n

L\u00e0 nh\u00e0 ph\u00e1t tri\u1ec3n, b\u1ea1n c\u00f3 th\u1ec3 \u0111\u1ec1 c\u1eadp \u0111\u1ebfn b\u1ea5t k\u1ef3 ho\u1ea1t \u0111\u1ed9ng c\u1ed9ng t\u00e1c n\u00e0o \u0111\u00e3 th\u1ef1c hi\u1ec7n v\u1edbi c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n kh\u00e1c trong qu\u00e1 kh\u1ee9 \u0111\u1ec3 \u0111\u1ea1t \u0111\u01b0\u1ee3c m\u1ee5c ti\u00eau c\u0169ng nh\u01b0 c\u00f4ng c\u1ee5 h\u1ecd \u0111\u00e3 s\u1eed d\u1ee5ng \u0111\u1ec3 giao ti\u1ebfp v\u1edbi c\u00e1c th\u00e0nh vi\u00ean kh\u00e1c trong nh\u00f3m.<\/p>\n

C\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n backend trung c\u1ea5p\u00a0<\/strong><\/h2>\n

6. Theo b\u1ea1n, nh\u01b0 th\u1ebf n\u00e0o l\u00e0 m\u1ed9t constructor? C\u00e1c lo\u1ea1i constructors l\u00e0 g\u00ec?<\/strong><\/h3>\n

Java s\u1eed d\u1ee5ng m\u1ed9t constructor \u0111\u1ec3 kh\u1edfi t\u1ea1o c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng. N\u00f3 \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng khi m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng trong m\u1ed9t l\u1edbp \u0111\u01b0\u1ee3c t\u1ea1o. M\u1ed9t constructor c\u00f3 c\u00f9ng t\u00ean v\u1edbi l\u1edbp c\u1ee7a n\u00f3. N\u00f3 c\u0169ng t\u01b0\u01a1ng t\u1ef1 v\u1ec1 m\u1eb7t c\u00fa ph\u00e1p nh\u01b0 m\u1ed9t ph\u01b0\u01a1ng th\u1ee9c. Tuy nhi\u00ean, constructor kh\u00f4ng c\u00f3 ki\u1ec3u tr\u1ea3 v\u1ec1 r\u00f5 r\u00e0ng.<\/p>\n

C\u00f3 ba lo\u1ea1i constructor ch\u00ednh:<\/p>\n

    \n
  • Default Constructor: Constructor kh\u00f4ng c\u00f3 \u0111\u1ed1i s\u1ed1. Ch\u00fang kh\u1edfi t\u1ea1o c\u00e1c th\u00e0nh vi\u00ean d\u1eef li\u1ec7u v\u1edbi c\u00e1c gi\u00e1 tr\u1ecb th\u1ef1c.<\/li>\n
  • Parameterized Constructor: Constructor ch\u1ee9a c\u00e1c \u0111\u1ed1i s\u1ed1. \u1ede \u0111\u00e2y ch\u00fang ta c\u00f3 th\u1ec3 v\u01b0\u1ee3t qua nhi\u1ec1u h\u01a1n m\u1ed9t \u0111\u1ed1i s\u1ed1.<\/li>\n
  • Copy constructor: Kh\u1edfi t\u1ea1o m\u1ed9t constructor b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng m\u1ed9t constructor kh\u00e1c c\u1ee7a c\u00f9ng m\u1ed9t l\u1edbp.<\/li>\n<\/ul>\n

    7. Ph\u00e2n bi\u1ec7t finally, final v\u00e0 finalize<\/strong><\/h3>\n

    Final l\u00e0 m\u1ed9t c\u00f4ng c\u1ee5 s\u1eeda \u0111\u1ed5i truy c\u1eadp, finally l\u00e0 m\u1ed9t block v\u00e0 finalize l\u00e0 m\u1ed9t ph\u01b0\u01a1ng th\u1ee9c c\u1ee7a m\u1ed9t l\u1edbp \u0111\u1ed1i t\u01b0\u1ee3ng. Finally \u0111\u01b0\u1ee3c th\u1ef1c thi khi \u0111\u01b0\u1ee3c g\u1ecdi. Final \u0111\u01b0\u1ee3c th\u1ef1c thi sau khi kh\u1ed1i try-catch \u0111\u01b0\u1ee3c th\u1ef1c thi. Vi\u1ec7c th\u1ef1c hi\u1ec7n n\u00f3 kh\u00f4ng ph\u1ee5 thu\u1ed9c v\u00e0o ngo\u1ea1i l\u1ec7. Cu\u1ed1i c\u00f9ng, finalize \u0111\u01b0\u1ee3c th\u1ef1c thi tr\u01b0\u1edbc khi \u0111\u1ed1i t\u01b0\u1ee3ng c\u00f3 th\u1ec3 b\u1ecb h\u1ee7y.<\/p>\n

    8. S\u1ef1 kh\u00e1c nhau gi\u1eefa Primitive Data Types v\u00e0 Wrapper Classes l\u00e0 g\u00ec?\u00a0<\/strong><\/h3>\n

    Wrapper Classes cho ph\u00e9p s\u1eed d\u1ee5ng nhi\u1ec1u ki\u1ec3u d\u1eef li\u1ec7u nguy\u00ean th\u1ee7y nh\u01b0 int ho\u1eb7c boolean l\u00e0m \u0111\u1ed1i t\u01b0\u1ee3ng. Wrapper Classes chuy\u1ec3n \u0111\u1ed5i Primitive Data th\u00e0nh m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng. Primitive Data Types l\u00e0 ki\u1ec3u d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh tr\u01b0\u1edbc m\u00e0 ng\u00f4n ng\u1eef l\u1eadp tr\u00ecnh Java cung c\u1ea5p.<\/p>\n

    9. C\u00e1c lo\u1ea1i threads kh\u00e1c nhau trong Java l\u00e0 g\u00ec?\u00a0<\/strong><\/h3>\n

    Thread l\u00e0 m\u1ed9t lu\u1ed3ng th\u1ef1c thi trong m\u1ed9t ch\u01b0\u01a1ng tr\u00ecnh. C\u00e1c thread cho ph\u00e9p c\u00e1c \u1ee9ng d\u1ee5ng Java ph\u1ea3n h\u1ed3i nhanh h\u01a1n v\u00e0 thu\u1eadn ti\u1ec7n h\u01a1n b\u1eb1ng c\u00e1ch th\u1ef1c hi\u1ec7n nhi\u1ec1u t\u00e1c v\u1ee5 c\u00f9ng m\u1ed9t l\u00fac.<\/p>\n

    C\u00f3 hai lo\u1ea1i thread: thread ng\u01b0\u1eddi d\u00f9ng v\u00e0 thread daemon. Thread daemon c\u00f3 m\u1ee9c \u0111\u1ed9 \u01b0u ti\u00ean th\u1ea5p v\u00e0 ch\u1ec9 cung c\u1ea5p d\u1ecbch v\u1ee5 cho c\u00e1c thread ng\u01b0\u1eddi d\u00f9ng. M\u1eb7t kh\u00e1c, thread ng\u01b0\u1eddi d\u00f9ng l\u00e0 thread c\u00f3 m\u1ee9c \u0111\u1ed9 \u01b0u ti\u00ean cao.<\/p>\n

    10. S\u1ef1 kh\u00e1c nhau gi\u1eefa MySQL v\u00e0 SQL l\u00e0 g\u00ec?<\/strong><\/h3>\n

    SQL (Structured Query Language) l\u00e0 ng\u00f4n ng\u1eef l\u1eadp tr\u00ecnh d\u00f9ng \u0111\u1ec3 giao ti\u1ebfp v\u1edbi c\u01a1 s\u1edf d\u1eef li\u1ec7u. MySQL l\u00e0 m\u1ed9t h\u1ec7 th\u1ed1ng qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 s\u1eed d\u1ee5ng SQL l\u00e0m ng\u00f4n ng\u1eef ch\u00ednh. SQL \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 t\u1ea1o, s\u1eeda \u0111\u1ed5i v\u00e0 x\u00f3a c\u01a1 s\u1edf d\u1eef li\u1ec7u, trong khi MySQL \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 l\u01b0u tr\u1eef v\u00e0 truy c\u1eadp d\u1eef li\u1ec7u trong c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/p>\n

    11. RDBMs l\u00e0 g\u00ec?\u00a0<\/strong><\/h3>\n

    H\u1ec7 th\u1ed1ng qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 (RDBMS) l\u00e0 m\u1ed9t ch\u01b0\u01a1ng tr\u00ecnh \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7. N\u00f3 \u0111\u00f3ng vai tr\u00f2 l\u00e0 n\u1ec1n t\u1ea3ng c\u1ee7a c\u00e1c h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u hi\u1ec7n \u0111\u1ea1i nh\u01b0 MySQL, Microsoft Access, Microsoft SQL Server v\u00e0 Oracle. RDBMS s\u1eed d\u1ee5ng SQL \u0111\u1ec3 l\u1ea5y d\u1eef li\u1ec7u t\u1eeb c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/p>\n

    12. C\u00e1c m\u1ec7nh \u0111\u1ec1 (clauses) ph\u1ed5 bi\u1ebfn nh\u1ea5t \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng trong truy v\u1ea5n SQL SELECT l\u00e0 g\u00ec?\u00a0<\/strong><\/h3>\n

    C\u00e1c m\u1ec7nh \u0111\u1ec1 SQL n\u00e0y th\u01b0\u1eddng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng v\u1edbi c\u00e2u l\u1ec7nh SELECT bao g\u1ed3m:<\/p>\n

      \n
    • FROM: ch\u1ec9 \u0111\u1ecbnh (c\u00e1c) b\u1ea3ng m\u00e0 d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c l\u1ea5y t\u1eeb \u0111\u00f3.<\/li>\n
    • WHERE: l\u1ecdc c\u00e1c b\u1ea3n ghi d\u1ef1a tr\u00ean c\u00e1c ti\u00eau ch\u00ed nh\u1ea5t \u0111\u1ecbnh.<\/li>\n
    • GROUP BY: nh\u00f3m c\u00e1c b\u1ea3n ghi d\u1ef1a tr\u00ean c\u00e1c ti\u00eau ch\u00ed nh\u1ea5t \u0111\u1ecbnh.<\/li>\n
    • HAVING: l\u1ecdc c\u00e1c b\u1ea3n ghi \u0111\u01b0\u1ee3c nh\u00f3m d\u1ef1a tr\u00ean c\u00e1c ti\u00eau ch\u00ed nh\u1ea5t \u0111\u1ecbnh.<\/li>\n
    • ORDER BY: s\u1eafp x\u1ebfp c\u00e1c b\u1ea3n ghi theo th\u1ee9 t\u1ef1 t\u0103ng d\u1ea7n ho\u1eb7c gi\u1ea3m d\u1ea7n.<\/li>\n
    • LIMIT gi\u1edbi h\u1ea1n s\u1ed1 l\u01b0\u1ee3ng b\u1ea3n ghi \u0111\u01b0\u1ee3c tr\u1ea3 v\u1ec1 t\u1eeb m\u1ed9t truy v\u1ea5n.<\/li>\n
    • OFFSET: ch\u1ec9 \u0111\u1ecbnh \u0111i\u1ec3m b\u1eaft \u0111\u1ea7u m\u00e0 c\u00e1c b\u1ea3n ghi \u0111\u01b0\u1ee3c tr\u1ea3 v\u1ec1.<\/li>\n
    • AS: t\u1ea1o b\u00ed danh cho t\u00ean c\u1ed9t ho\u1eb7c t\u00ean b\u1ea3ng.<\/li>\n
    • JOIN: k\u1ebft h\u1ee3p c\u00e1c b\u1ea3n ghi t\u1eeb hai ho\u1eb7c nhi\u1ec1u b\u1ea3ng.<\/li>\n
    • UNION: k\u1ebft h\u1ee3p t\u1eadp h\u1ee3p k\u1ebft qu\u1ea3 c\u1ee7a hai ho\u1eb7c nhi\u1ec1u truy v\u1ea5n CH\u1eccN.<\/li>\n<\/ul>\n

      13. S\u1ef1 kh\u00e1c nhau gi\u1eefa statistic website v\u00e0 dynamic website l\u00e0 g\u00ec?\u00a0<\/strong><\/h3>\n

      C\u00e1c trang web t\u0129nh (statistic website) c\u00f3 n\u1ed9i dung c\u1ed1 \u0111\u1ecbnh, ngh\u0129a l\u00e0 n\u00f3 s\u1ebd kh\u00f4ng \u0111\u01b0\u1ee3c c\u1eadp nh\u1eadt th\u01b0\u1eddng xuy\u00ean. N\u1ed9i dung \u0111\u01b0\u1ee3c m\u00e3 h\u00f3a tr\u1ef1c ti\u1ebfp v\u00e0o HTML v\u00e0 y\u00eau c\u1ea7u c\u1eadp nh\u1eadt th\u1ee7 c\u00f4ng khi c\u1ea7n thay \u0111\u1ed5i. Trang web \u0111\u1ed9ng (dynamic website) l\u00e0 nh\u1eefng trang web c\u00f3 n\u1ed9i dung \u0111\u01b0\u1ee3c c\u1eadp nh\u1eadt th\u01b0\u1eddng xuy\u00ean v\u00e0 t\u1ef1 \u0111\u1ed9ng.<\/p>\n

      C\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n backend n\u00e2ng cao\u00a0<\/strong><\/h2>\n

      14. N\u00eau s\u1ef1 kh\u00e1c nhau c\u1ee7a 2 lo\u1ea1i bi\u1ebfn trong Python: Global v\u00e0 Local<\/strong><\/h3>\n

      Bi\u1ebfn Global \u0111\u01b0\u1ee3c khai b\u00e1o b\u00ean ngo\u00e0i h\u00e0m ho\u1eb7c trong kh\u00f4ng gian Global. C\u00e1c bi\u1ebfn n\u00e0y c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c truy c\u1eadp t\u1eeb b\u1ea5t k\u1ef3 ch\u1ee9c n\u0103ng n\u00e0o trong ch\u01b0\u01a1ng tr\u00ecnh.<\/p>\n

      Bi\u1ebfn Local l\u00e0 b\u1ea5t k\u1ef3 bi\u1ebfn n\u00e0o \u0111\u01b0\u1ee3c khai b\u00e1o trong m\u1ed9t h\u00e0m. Bi\u1ebfn n\u00e0y ch\u1ec9 hi\u1ec7n di\u1ec7n trong kh\u00f4ng gian Local.<\/p>\n

      15. S\u1ef1 kh\u00e1c nhau gi\u1eefa m\u1ea3ng v\u00e0 danh s\u00e1ch trong Python l\u00e0 g\u00ec?\u00a0<\/strong><\/h3>\n

      M\u1ea3ng Python t\u01b0\u01a1ng t\u1ef1 nh\u01b0 danh s\u00e1ch \u1edf ch\u1ed7 c\u1ea3 hai \u0111\u1ec1u \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 l\u01b0u tr\u1eef nhi\u1ec1u gi\u00e1 tr\u1ecb. Tuy nhi\u00ean, kh\u00f4ng gi\u1ed1ng nh\u01b0 danh s\u00e1ch, m\u1ea3ng \u0111\u01b0\u1ee3c gi\u1edbi h\u1ea1n \u1edf m\u1ed9t ki\u1ec3u d\u1eef li\u1ec7u duy nh\u1ea5t v\u00e0 c\u00f3 k\u00edch th\u01b0\u1edbc c\u1ed1 \u0111\u1ecbnh. Ngo\u00e0i ra, m\u1ea3ng s\u1eed d\u1ee5ng b\u1ed9 nh\u1edb hi\u1ec7u qu\u1ea3 h\u01a1n nhi\u1ec1u so v\u1edbi danh s\u00e1ch v\u00ec ch\u00fang ch\u1ec9 l\u01b0u tr\u1eef c\u00e1c gi\u00e1 tr\u1ecb c\u1ee7a m\u1ed9t lo\u1ea1i duy nh\u1ea5t.<\/p>\n

      16. NULL l\u00e0 g\u00ec?\u00a0<\/strong><\/h3>\n

      Ki\u1ec3u d\u1eef li\u1ec7u NULL l\u00e0 ki\u1ec3u d\u1eef li\u1ec7u m\u1ed9t gi\u00e1 tr\u1ecb \u0111\u1eb7c bi\u1ec7t. M\u1ed9t bi\u1ebfn ki\u1ec3u d\u1eef li\u1ec7u NULL l\u00e0 m\u1ed9t bi\u1ebfn kh\u00f4ng c\u00f3 gi\u00e1 tr\u1ecb. N\u00f3 c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c ch\u1ec9 \u0111\u1ecbnh b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng nh\u01b0 sau: $var = NULL; ho\u1eb7c $var = null;<\/p>\n

      17. PHP v\u00e0 HTML t\u01b0\u01a1ng t\u00e1c v\u1edbi nhau nh\u01b0 th\u1ebf n\u00e0o?\u00a0<\/strong><\/h3>\n

      B\u1ea1n c\u00f3 th\u1ec3 t\u1ea1o HTML b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng t\u1eadp l\u1ec7nh PHP. Ngo\u00e0i ra, b\u1ea1n c\u00f3 th\u1ec3 chuy\u1ec3n th\u00f4ng tin t\u1eeb HTML sang PHP. PHP th\u1ef1c thi tr\u00ean m\u00e1y ch\u1ee7 v\u00e0 tr\u1ea3 v\u1ec1 k\u1ebft qu\u1ea3 c\u1ee7a n\u00f3 \u1edf d\u1ea1ng chu\u1ed7i, m\u1ea3ng v\u00e0 \u0111\u1ed1i t\u01b0\u1ee3ng. Sau \u0111\u00f3, ch\u00fang s\u1ebd hi\u1ec3n th\u1ecb c\u00e1c gi\u00e1 tr\u1ecb \u0111\u00e3 \u0111\u1ec1 c\u1eadp trong HTML.<\/p>\n

      18. Python t\u1ea1o ra s\u1ed1 ng\u1eabu nhi\u00ean b\u1eb1ng c\u00e1ch n\u00e0o?\u00a0<\/strong><\/h3>\n

      Trong Python, b\u1ea1n c\u00f3 th\u1ec3 t\u1ea1o ra c\u00e1c s\u1ed1 ng\u1eabu nhi\u00ean b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng module random. Module random cung c\u1ea5p m\u1ed9t s\u1ed1 h\u00e0m \u0111\u1ec3 t\u1ea1o ra c\u00e1c s\u1ed1 ng\u1eabu nhi\u00ean v\u1edbi c\u00e1c lo\u1ea1i kh\u00e1c nhau. D\u01b0\u1edbi \u0111\u00e2y l\u00e0 m\u1ed9t s\u1ed1 h\u00e0m ph\u1ed5 bi\u1ebfn:<\/p>\n

        \n
      • random.random(): H\u00e0m n\u00e0y tr\u1ea3 v\u1ec1 m\u1ed9t s\u1ed1 th\u1ef1c ng\u1eabu nhi\u00ean trong kho\u1ea3ng t\u1eeb 0 \u0111\u1ebfn 1.<\/li>\n
      • random.randint(a, b): H\u00e0m n\u00e0y tr\u1ea3 v\u1ec1 m\u1ed9t s\u1ed1 nguy\u00ean ng\u1eabu nhi\u00ean trong kho\u1ea3ng t\u1eeb a \u0111\u1ebfn b (bao g\u1ed3m c\u1ea3 a v\u00e0 b).<\/li>\n
      • random.uniform(a, b): H\u00e0m n\u00e0y tr\u1ea3 v\u1ec1 m\u1ed9t s\u1ed1 th\u1ef1c ng\u1eabu nhi\u00ean trong kho\u1ea3ng t\u1eeb a \u0111\u1ebfn b.<\/li>\n
      • random.choice(sequence): H\u00e0m n\u00e0y tr\u1ea3 v\u1ec1 m\u1ed9t ph\u1ea7n t\u1eed ng\u1eabu nhi\u00ean t\u1eeb d\u00e3y \u0111\u01b0\u1ee3c cung c\u1ea5p, nh\u01b0 m\u1ed9t list hay m\u1ed9t chu\u1ed7i.<\/li>\n
      • random.shuffle(sequence): H\u00e0m n\u00e0y x\u00e1o tr\u1ed9n ng\u1eabu nhi\u00ean c\u00e1c ph\u1ea7n t\u1eed trong d\u00e3y \u0111\u01b0\u1ee3c cung c\u1ea5p.<\/li>\n<\/ul>\n

        \u0110\u1ec3 s\u1eed d\u1ee5ng c\u00e1c h\u00e0m n\u00e0y, b\u1ea1n c\u1ea7n import module random \u1edf \u0111\u1ea7u c\u1ee7a script Python ho\u1eb7c phi\u00ean t\u01b0\u01a1ng t\u00e1c. V\u00ed d\u1ee5:<\/p>\n

        import random\n\n# T\u1ea1o m\u1ed9t s\u1ed1 th\u1ef1c ng\u1eabu nhi\u00ean trong kho\u1ea3ng t\u1eeb 0 \u0111\u1ebfn 1\n\nso_ngau_nhien = random.random()\n\n# T\u1ea1o m\u1ed9t s\u1ed1 nguy\u00ean ng\u1eabu nhi\u00ean trong kho\u1ea3ng t\u1eeb 1 \u0111\u1ebfn 100\n\nso_nguyen_ngau_nhien = random.randint(1, 100)\n\n# T\u1ea1o m\u1ed9t s\u1ed1 th\u1ef1c ng\u1eabu nhi\u00ean trong kho\u1ea3ng t\u1eeb -1 \u0111\u1ebfn 1\n\nso_thuc_ngau_nhien = random.uniform(-1, 1)\n\n# Ch\u1ecdn ng\u1eabu nhi\u00ean m\u1ed9t ph\u1ea7n t\u1eed t\u1eeb m\u1ed9t list\n\ndanh_sach_cua_toi = [1, 2, 3, 4, 5]\n\nphuong_an_ngau_nhien = random.choice(danh_sach_cua_toi)\n\n# X\u00e1o tr\u1ed9n c\u00e1c ph\u1ea7n t\u1eed trong m\u1ed9t list\n\nrandom.shuffle(danh_sach_cua_toi)<\/code><\/pre>\n
        \u0110\u00e2y ch\u1ec9 l\u00e0 m\u1ed9t s\u1ed1 v\u00ed d\u1ee5 v\u1ec1 c\u00e1ch t\u1ea1o ra c\u00e1c s\u1ed1 ng\u1eabu nhi\u00ean trong Python b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng module random. Module random cung c\u1ea5p th\u00eam nhi\u1ec1u h\u00e0m v\u00e0 t\u00f9y ch\u1ecdn t\u00f9y ch\u1ec9nh kh\u00e1c \u0111\u1ec3 t\u1ea1o ra d\u1eef li\u1ec7u ng\u1eabu nhi\u00ean.<\/p>\n
        19. C\u00e1c lo\u1ea1i m\u1ea3ng (arrays) kh\u00e1c nhau trong PHP l\u00e0 g\u00ec?\u00a0<\/strong><\/h3>\n
        C\u00f3 ba lo\u1ea1i m\u1ea3ng (arrays) c\u00f3 s\u1eb5n trong PHP:<\/p>\n
          \n
        • M\u1ea3ng \u0111\u01b0\u1ee3c l\u1eadp ch\u1ec9 m\u1ee5c \u2013 M\u1ed9t m\u1ea3ng c\u00f3 ch\u1ec9 s\u1ed1 b\u1eb1ng s\u1ed1 \u0111\u01b0\u1ee3c g\u1ecdi l\u00e0 m\u1ea3ng \u0111\u01b0\u1ee3c l\u1eadp ch\u1ec9 m\u1ee5c. C\u00e1c gi\u00e1 tr\u1ecb \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef theo th\u1ee9 t\u1ef1 tuy\u1ebfn t\u00ednh v\u00e0 c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c truy c\u1eadp b\u1eb1ng c\u00e1c ph\u01b0\u01a1ng ti\u1ec7n tuy\u1ebfn t\u00ednh.<\/li>\n
        • M\u1ea3ng k\u1ebft h\u1ee3p \u2013 M\u1ed9t m\u1ea3ng bao g\u1ed3m c\u00e1c chu\u1ed7i l\u00e0m ch\u1ec9 m\u1ee5c c\u00f2n \u0111\u01b0\u1ee3c g\u1ecdi l\u00e0 m\u1ea3ng k\u1ebft h\u1ee3p. \u0110i\u1ec1u n\u00e0y l\u01b0u tr\u1eef c\u00e1c gi\u00e1 tr\u1ecb ph\u1ea7n t\u1eed li\u00ean k\u1ebft v\u1edbi c\u00e1c gi\u00e1 tr\u1ecb ch\u00ednh, thay v\u00ec theo th\u1ee9 t\u1ef1 ch\u1ec9 m\u1ee5c tuy\u1ebfn t\u00ednh nghi\u00eam ng\u1eb7t.<\/li>\n
        • M\u1ea3ng \u0111a chi\u1ec1u \u2013 M\u1ed9t m\u1ea3ng nhi\u1ec1u chi\u1ec1u ch\u1ee9a m\u1ed9t ho\u1eb7c nhi\u1ec1u m\u1ea3ng. \u1ede \u0111\u00e2y, nhi\u1ec1u ch\u1ec9 s\u1ed1 \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 truy c\u1eadp c\u00e1c gi\u00e1 tr\u1ecb.<\/li>\n<\/ul>\n
          20. Type hinting trong PHP l\u00e0 g\u00ec<\/strong><\/h3>\n
          Type hinting \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 x\u00e1c \u0111\u1ecbnh ki\u1ec3u d\u1eef li\u1ec7u d\u1ef1 ki\u1ebfn cho m\u1ed9t \u0111\u1ed1i s\u1ed1 trong khai b\u00e1o h\u00e0m. Khi b\u1ea1n g\u1ecdi n\u00f3, PHP s\u1ebd x\u00e1c \u0111\u1ecbnh xem c\u00e1c \u0111\u1ed1i s\u1ed1 c\u00f3 thu\u1ed9c lo\u1ea1i \u0111\u01b0\u1ee3c ch\u1ec9 \u0111\u1ecbnh hay kh\u00f4ng. N\u1ebfu kh\u00f4ng, th\u1eddi gian ch\u1ea1y s\u1ebd hi\u1ec3n th\u1ecb l\u1ed7i v\u00e0 qu\u00e1 tr\u00ecnh th\u1ef1c thi s\u1ebd d\u1eebng l\u1ea1i.<\/p>\n
          K\u1ebft lu\u1eadn<\/strong><\/h2>\n
          V\u1eady l\u00e0 Masterskills \u0111\u00e3 c\u00f9ng b\u1ea1n t\u00ecm hi\u1ec3u top 20 c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n Backend<\/strong> th\u01b0\u1eddng g\u1eb7p nh\u1ea5t. Hy v\u1ecdng nh\u1eefng g\u1ee3i \u00fd tr\u00ean s\u1ebd gi\u00fap b\u1ea1n c\u00f3 \u0111\u01b0\u1ee3c s\u1ef1 chu\u1ea9n b\u1ecb t\u1ed1t nh\u1ea5t cho bu\u1ed5i ph\u1ecfng v\u1ea5n s\u1eafp t\u1edbi. N\u1ebfu c\u1ea3m th\u1ea5y h\u1ee9ng th\u00fa v\u1edbi c\u00e1c ch\u1ee7 \u0111\u1ec1 t\u01b0\u01a1ng t\u1ef1, h\u00e3y gh\u00e9 qua Blog c\u1ee7a Masterskills \u0111\u1ec3 c\u1eadp nh\u1eadt th\u00eam nhi\u1ec1u n\u1ed9i dung ch\u1ea5t l\u01b0\u1ee3ng kh\u00e1c nh\u00e9!<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"
          Backend l\u00e0 x\u01b0\u01a1ng s\u1ed1ng c\u1ee7a c\u00e1c \u1ee9ng d\u1ee5ng web, x\u1eed l\u00fd x\u1eed l\u00fd d\u1eef li\u1ec7u, logic ph\u00eda m\u00e1y ch\u1ee7 v\u00e0 qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u. \u0110\u1ec3 v\u01b0\u1ee3t qua c\u00e1c cu\u1ed9c ph\u1ecfng v\u1ea5n Backend kh\u00f3 nh\u1eb1n, b\u1ea1n ph\u1ea3i c\u00f3 hi\u1ec3u bi\u1ebft v\u1eefng ch\u1eafc v\u1ec1 c\u00e1c kh\u00e1i ni\u1ec7m v\u00e0 nguy\u00ean t\u1eafc c\u01a1 b\u1ea3n trong l\u0129nh v\u1ef1c […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[181],"tags":[],"_links":{"self":[{"href":"https:\/\/masterskills.org\/blog\/wp-json\/wp\/v2\/posts\/49973"}],"collection":[{"href":"https:\/\/masterskills.org\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/masterskills.org\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/masterskills.org\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/masterskills.org\/blog\/wp-json\/wp\/v2\/comments?post=49973"}],"version-history":[{"count":0,"href":"https:\/\/masterskills.org\/blog\/wp-json\/wp\/v2\/posts\/49973\/revisions"}],"wp:attachment":[{"href":"https:\/\/masterskills.org\/blog\/wp-json\/wp\/v2\/media?parent=49973"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/masterskills.org\/blog\/wp-json\/wp\/v2\/categories?post=49973"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/masterskills.org\/blog\/wp-json\/wp\/v2\/tags?post=49973"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}