Video: Cov ntaub ntawv li cas thaum txhais hauv SQL?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Cov SQL CASE Statement
Cov CASE lus mus los ntawm tej yam kev mob thiab xa rov qab tus nqi thaum thawj mob tau ntsib (zoo li IF- THEN-ELSE nqe lus ). Yog li, ib zaug ib mob muaj tseeb, nws yuav tsum tsis txhob nyeem ntawv thiab rov qab cov txiaj ntsig. Yog tias tsis muaj cov xwm txheej muaj tseeb, nws rov qab los tus nqi hauv ELSE clause.
Tom qab ntawd, ib tus tuaj yeem nug, ua li cas koj sau cov ntaub ntawv hauv SQL?
Cov CASE lus tuaj yeem siv hauv SQL ntawv Server (Kev hloov pauv- SQL ntawv ). SELECT contact_id, CAS THAUM lub website_id = 1 TAM SIM NO 'TechOnTheNet.com' THAUM lub vev xaib_id = 2 TAM SIM NO 'CheckYourMath.com' LEEJ TWG 'BigActivities.com' NTAU NTAWM cov neeg sib cuag; Ib yam uas yuav tsum nco ntsoov yog qhov ELSE mob nyob rau hauv CASE lus yog xaiv tau.
Dab tsi yog rooj plaub thiab txiav txim siab hauv SQL? Qhov txawv ntawm CASE thiab DeCODE yog.:- CAS yog ib nqe lus uas yog DECODE yog ib txoj haujlwm.:- CAS tuaj yeem siv rau hauv ob qho tib si SQL ntawv thiab PLSQL. Tab sis DECODE tuaj yeem siv tsuas yog hauv SQL ntawv .:- CAS siv nyob rau hauv qhov twg clause Tab sis koj siv tsis tau DECODE nyob qhov twg clause.
Cov lus nug tseem yog, cov ntaub ntawv hais txog dab tsi ua?
CASE Statement . Cov CASE lus xaiv los ntawm ib theem zuj zus ntawm tej yam kev mob, thiab executes ib tug coj nqe lus . Cov CASE lus ntsuas ib leeg kev qhia thiab muab piv rau ntau qhov muaj peev xwm, lossis ntsuas ntau yam Boolean kab lus thiab xaiv thawj tus uas yog TRUE.
Koj puas tuaj yeem ua yog tias cov nqe lus hauv SQL?
Hauv MS SQL ntawv , IF … LUS yog hom Cov lus qhia . Ib T- SQL nqe lus tuaj yeem yuav tsum ua raws li kev siv IF … ELSE . Yog qhov xwm txheej ntsuas qhov tseeb, ces T- SQL lus ua raws li IF lo lus tseem ceeb yuav raug tua.
Pom zoo:
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