Limit ua dab tsi hauv SQL?

2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47

Cov SQL ntawv Xaiv TXOJ CAI nqe lus yog siv los muab cov ntaub ntawv los ntawm ib lossis ntau lub rooj hauv ib lub database thiab txwv tus naj npawb ntawm cov ntaub ntawv xa rov qab raws li a txwv tus nqi. TSWV YIM: SELECT TXOJ CAI tsis txaus siab nyob rau hauv tag nrho SQL ntawv databases. Rau databases xws li SQL ntawv Server lossis MSaccess, siv SELECT TOP nqe lus rau txwv koj cov qhabnias.

Hais txog qhov no, kev txwv kev ua haujlwm li cas hauv SQL?

SQL | LIMIT Clause

• LIMIT clause yog siv los teeb tsa qhov txwv siab ntawm tus naj npawb ntawm tuples rov qab los ntawm SQL.
• Nws yog ib qho tseem ceeb uas yuav tsum nco ntsoov tias cov kab lus no tsis txhawb nqa los ntawm txhua tus SQL versions.
• LIMIT clause kuj tseem tuaj yeem teev tseg siv SQL 2008 OFFSET/FETCH FIRST clauses.
• Cov kev txwv/offset kab lus yuav tsum yog ib tug tsis-negative integer.

Tsis tas li, qhov txwv hauv DBMS yog dab tsi? Cov txwv lo lus tseem ceeb yog siv rau txwv tus naj npawb ntawm kab rov qab rau hauv cov lus nug tshwm sim. Yog tias cov ntaub ntawv hauv cov lus teev tsawg dua N, ces tag nrho cov ntaub ntawv los ntawm cov lus nug raug xa rov qab rau hauv qhov tshwm sim.

Kuj Paub, dab tsi yog txwv thiab offset hauv SQL?

Taw qhia rau SQL LIMIT clause Lub row_count txiav txim seb tus naj npawb ntawm kab uas yuav rov qab los. Cov OFFSET clause hla lub offset kab ua ntej pib rov qab kab. Cov OFFSET clause yog xaiv tau yog li koj tuaj yeem hla nws.

Kuv yuav xaiv 3 kab saum toj kawg nkaus hauv SQL li cas?

SQL SELECT TOP Clause

1. SQL Server / MS Access Syntax: SELECT TOP naj npawb|feem pua npe column_name(s) FROM table_name. Qhov twg mob;
2. MySQL Syntax: SELECT column_name(s) NTAWM table_name. Qhov twg mob. LIMIT tus lej;
3. Oracle Syntax: SELECT column_name(s) NTAWM table_name. THAUM ROWNUM <= tus lej;