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Wildcard SQL Server yog dab tsi?
Wildcard SQL Server yog dab tsi?

Video: Wildcard SQL Server yog dab tsi?

Video: Wildcard SQL Server yog dab tsi?
Video: SQL Tutorial - Full Database Course for Beginners 2024, Kaum ib hlis
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SQL Wildcards

A daim ntawv qub tus cwj pwm yog siv los hloov ib lossis ntau tus cim hauv ib txoj hlua. Wildcard cov cim yog siv nrog cov SQL ntawv LIKE tus neeg ua haujlwm. Tus neeg teb xov tooj LIKE yog siv nyob rau hauv ib lo lus nyob qhov twg los tshawb nrhiav tus qauv qhia hauv kab.

Tsis tas li cov lus nug yog, dab tsi yog lub cim wildcard hauv SQL Server?

Lub underscore (_) daim ntawv qub : ib tus cim. [list of character] daim ntawv qub : txhua tus cim ib leeg nyob rau hauv qhov teev. Tus [tus cwj pwm-tus cwj pwm]: ib tus cwj pwm ib leeg hauv qhov kev teev tseg. Tus [^]: ib tus cim tsis nyob hauv ib daim ntawv lossis ib qho.

Ib tug kuj tseem nug, * txhais li cas hauv SQL? Hauv SQL ntawv * txhais tau tias Tag nrho cov ntaub ntawv, tsis tsuas yog nyob rau hauv SQL ntawv hauv lwm yam lus programming * hu ua wild card cim uas txhais tau tias tag nrho cov ntaub ntawv tam sim no. Hauv SQL ntawv peb siv * nrog SELECT query los xaiv tag nrho cov ntaub ntawv teev cov lus xav tau.

Tib neeg kuj nug, ua li cas koj sau ib tus tsiaj qus hauv SQL?

SQL cov ntaub ntawv yog siv los tshawb nrhiav cov ntaub ntawv hauv ib lub rooj.

SQL Wildcard Cov cim.

Wildcard Kev piav qhia
% Ib qho kev hloov pauv rau xoom lossis ntau tus cim
_ Ib tug hloov rau ib tug cim
[charlist] Teeb thiab ntau ntawm cov cim kom phim
[^charlist] lossis [!charlist] Matches tsuas yog ib tug cim TSIS tau teev nyob rau hauv lub brackets

Kev siv SQL yog dab tsi?

SQL ntawv yog siv sib txuas lus nrog ib tug database. Raws li ANSI (American National Standards Institute), nws yog tus qauv lus rau kev sib raug zoo database tswj systems. SQL ntawv nqe lus yog siv los ua cov haujlwm xws li hloov kho cov ntaub ntawv ntawm cov ntaub ntawv, lossis khaws cov ntaub ntawv los ntawm cov ntaub ntawv.

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