Txhua lub rooj yuav tsum muaj tus yuam sij tseem ceeb?
Txhua lub rooj yuav tsum muaj tus yuam sij tseem ceeb?

Video: Txhua lub rooj yuav tsum muaj tus yuam sij tseem ceeb?

Video: Txhua lub rooj yuav tsum muaj tus yuam sij tseem ceeb?
Video: Yasmi - Yog Muaj Ib Hnub 2024, Kaum ib hlis
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Txhua lub rooj ua tau muaj (tab sis ua tsis yog muaj rau muaj) qhov tseem ceeb . Cov kab los yog kab lus txhais raws li tus thawj tus yuam sij xyuas kom uniqueness nyob rau hauv lub rooj ; tsis muaj ob kab ua tau muaj tib yam tus yuam sij . Cov thawj tus yuam sij ntawm ib rooj kuj tseem yuav pab txheeb xyuas cov ntaub ntawv hauv lwm yam rooj , thiab ua ib feem ntawm qhov thib ob lub rooj tseem ceeb.

Ntxiv mus, txhua lub rooj yuav tsum muaj lub ntsiab tseem ceeb?

Txhua lub rooj nyob rau hauv ib tug relational database yuav tsum muaj qhov tseem ceeb . Cov thawj tus yuam sij yog ib kem, los yog kab ke, uas tso cai rau txhua kab hauv lub rooj kom paub qhov txawv. Tsis muaj ob kab hauv ib rooj nrog a thawj tus yuam sij ua tau muaj tib yam thawj tus yuam sij tus nqi.

Tsis tas li ntawd, puas yog Primary Key yuam hauv SQL? Koj tuaj yeem siv UNIQUE (kev txwv tsis yog qhov ntsuas) thiab TSIS TXHOB ua ke los tswj hwm yuam sij hauv SQL ntawv . Yog li ntawd, tsis yog, a thawj tus yuam sij (los yog TSEEM CEEB ) tsis tsim nyog nyob rau hauv SQL ntawv Server.

Raws li txoj cai, peb puas tuaj yeem muaj rooj tsis muaj tus yuam sij tseem ceeb?

Tsis yog. Txhua rooj yuav tsum muaj qee kem (los yog cov kab ke) uas qhia txog ib qho thiab tsuas yog ib kab xwb. Nws ua rau nws yooj yim dua los tswj cov ntaub ntawv. Nws muaj tseeb, tsis muaj a thawj tus yuam sij (los yog qee qhov tshwj xeeb tus yuam sij ), koj tsis txhob muaj ib qho kev ntxig anomaly yog tias koj mus rau ntxig tib cov ntaub ntawv ntau zaus.

Yuav muaj pes tsawg tus yuam sij tseem ceeb hauv lub rooj?

ib qho tseem ceeb

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