Cov txheej txheem:
Video: Nocheck txwv SQL Server yog dab tsi?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Nrog TSIS TAU ua li ntawd yam tsis tau txheeb xyuas cov ntaub ntawv uas twb muaj lawm. Yog li qhov tsis meej pem syntax WITH TSIS TAU KOOB CONSTRAINT enables ib txwv tsis kuaj xyuas cov ntaub ntawv uas twb muaj lawm. Qhia meej seb cov ntaub ntawv hauv lub rooj puas yog lossis tsis raug lees paub tiv thaiv ib qho tshiab ntxiv lossis rov qhib FOREIGN KEY lossis CHECK txwv.
Tom qab ntawd, Kuv yuav ua li cas thiaj li pab tau cov kev txwv hauv SQL Server?
Pab a Tshawb xyuas kev txwv Lub syntax rau ua haujlwm a xyuas qhov txwv hauv SQL Server (Kev lag luam- SQL ntawv ) yog: ALTER TABLE table_name WITH CHECK CONSTRAINT constraint_name; table_npe. Lub npe ntawm lub rooj uas koj xav tau pab tus check txwv.
Ib yam li ntawd, dab tsi yog tswj hwm txawv teb chaws qhov tseem ceeb hauv SQL? Txawv Teb Chaws Tseem Ceeb . A txawv teb chaws key (FK) yog ib kem lossis ua ke ntawm kab uas siv los tsim thiab yuam ib qho kev sib txuas ntawm cov ntaub ntawv hauv ob lub rooj los tswj cov ntaub ntawv uas tuaj yeem khaws cia rau hauv lub txawv teb chaws key rooj.
Hais txog qhov no, kuv yuav ua li cas kaw cov kev txwv hauv SQL?
Siv SQL Server Management Studio
- Hauv Object Explorer, nthuav lub rooj nrog qhov txwv thiab tom qab ntawd nthuav cov Keys folder.
- Right-click qhov txwv thiab xaiv Hloov Kho.
- Nyob rau hauv daim phiaj nyob rau hauv Table Designer, nias Enforce Foreign Key Constraint thiab xaiv Tsis yog los ntawm cov ntawv qhia zaub mov nco-down.
- Nyem Kaw.
Dab tsi yog check constraint nyob rau hauv database?
A check txwv yog hom kev ncaj ncees txwv hauv SQL uas qhia meej txog qhov yuav tsum tau ua los ntawm txhua kab hauv a database rooj. Cov txwv yuav tsum yog ib tug predicate. Tshawb xyuas cov kev txwv yog siv los xyuas kom meej qhov siv tau ntawm cov ntaub ntawv hauv a database thiab muab cov ntaub ntawv ncaj ncees.
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