Video: Kev siv ENUM hauv MySQL yog dab tsi?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Hauv MySQL, ib qho ENUM yog ib txoj hlua khoom uas nws tus nqi raug xaiv los ntawm cov npe ntawm cov nqi tso cai tau teev tseg thaum lub sijhawm tsim kab. Hom ENUM cov ntaub ntawv muab cov hauv qab no qhov zoo : Compact data khaws cia . MySQL ENUM siv numeric indexes (1, 2, 3, …) los sawv cev rau stringvalues.
Raws li, enums siv rau dab tsi?
Kev suav sau (los yog enum ) yog tus neeg siv txhais cov ntaub ntawv hauv C. Nws yog feem ntau siv rau muab cov npe rau qhov tsis tu ncua, cov npe ua kom yooj yim nyeem thiab khaws cia. enum Xeev {Ua haujlwm = 1, Ua tsis tiav = 0}; Lo lus tseem ceeb' enum 'yog siv rau tshaj tawm tshiab kev suav sau hom hauv C thiab C ++.
Ib sab saum toj no, enum sawv rau dab tsi? ENUM sawv rau xov tooj daim ntawv qhia. Nws yog qhov yooj yim plaub tsab ntawv acronym sawv cev rau lub tswv yim tseem ceeb: siv tau tib tus xov tooj txawm tias koj nyob qhov twg hauv ntiaj teb.
Secondly, dab tsi yog enum nrog piv txwv?
Lwm yam piv txwv suav nrog cov xwm txheej suav nrog (xws li lub ntiaj teb, hnub ntawm lub lim tiam, xim, cov lus qhia, thiab lwm yam). Nws tsis yog qhov tsim nyog uas cov txheej txheem tas mus li hauv ib qho enum typestay tsau rau txhua lub sijhawm. Hauv Java (los ntawm 1.5), enums sawv cev siv enum hom ntaub ntawv.
Vim li cas peb thiaj siv enum hauv C#?
Hauv C# , enum yog tus nqi hom ntaub ntawv hom. Cov enum yog siv tshaj tawm ib daim ntawv teev npe integerconstants. Nws tuaj yeem txhais tau siv tus enum lo lus tseem ceeb ncaj qha hauv lub npe, chav kawm, lossis qauv. Cov enum yog siv muab lub npe rau txhua qhov tas mus li kom tus constantineger tuaj yeem raug xa mus siv nws lub npe.
Pom zoo:
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