CTE yog dab tsi hauv SQL Server?

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

A CTE ( Common Table Expression ) yog ib qho kev tshwm sim ib ntus uas koj tuaj yeem xa mus rau lwm qhov SELECT, INSERT, UPDATE, lossis DELETE nqe lus. Lawv tau qhia hauv SQL Server version 2005.

Tom qab ntawd, ib tus tuaj yeem nug, CTE yog dab tsi hauv SQL Server thiab nws siv?

SQL Server CTE Cov hauv paus. Taw qhia hauv SQL Server 2005, cov lus qhia dav dav ( CTE ) yog lub npe teev npe ib ntus uas koj tuaj yeem siv hauv SELECT, INSERT, UPDATE, lossis DELETE nqe lus. Koj tuaj yeem ua tau siv a CTE hauv daim ntawv CREATE VIEW, uas yog ib feem ntawm tus saib SELECT nug.

Tsis tas li ntawd, dab tsi yog recursive CTE hauv SQL Server? Taw qhia rau SQL Server recursive CTE A recursive common table expression ( CTE ) yog a CTE uas references nws tus kheej. Los ntawm kev ua li ntawd, lub CTE rov executes, rov qab subsets ntawm cov ntaub ntawv, kom txog rau thaum nws rov qab ua tiav cov txheej txheem.

Kuj nug, vim li cas CTE siv hauv SQL Server?

Vim li cas rau siv a CTE Hauv SQL ntawv , peb yuav siv sub-queries los koom nrog cov ntaub ntawv los yog lim cov ntaub ntawv los ntawm cov lus nug sub. Thaum twg peb xa tib cov ntaub ntawv lossis koom nrog tib cov ntaub ntawv siv cov lus nug, cov cai tswj xyuas yuav nyuaj. A CTE ua kom zoo nyeem ntawv thiab kev saib xyuas yooj yim dua.

Kuv yuav siv ob CTE li cas hauv SQL?

Rau siv ntau CTE's nyob rau hauv ib qho lus nug koj tsuas yog yuav tsum ua kom tiav thawj zaug CTE , ntxiv ib qho comma, tshaj tawm lub npe thiab xaiv kab rau lwm qhov CTE , qhib CTE query nrog ib tug comma, sau cov lus nug, thiab nkag tau los ntawm a CTE cov lus nug tom qab hauv tib cov lus nug lossis los ntawm cov lus nug zaum kawg sab nraum CTEs.