Cov txheej txheem:

Custered index yuav tsis txawv?
Custered index yuav tsis txawv?
Anonim

Ob pawg thiab tsis suav nrog tuaj yeem yog qhov tshwj xeeb. Qhov no txhais tau tias tsis muaj ob kab tuaj yeem muaj tus nqi tib yam rau tus yuam sij index. Txwv tsis pub, qhov Performance index tsis yog qhov tshwj xeeb thiab ntau kab tuaj yeem faib cov nqi tseem ceeb. Yog xav paub ntxiv, saib Tsim Cov Ntawv Qhia Tshwj Xeeb.

Yuav ua li cas sib koom ua ke tso cai duplicates?

Yog, koj tuaj yeem tsim qhov ntsuas ntsuas ntawm cov kab tseem ceeb uas muaj qhov sib npaug. … Piv txwv li, tej zaum koj yuav txiav txim siab los tsim ib qho kev ntsuas ntawm pawg LastName ntawm lub rooj uas muaj cov neeg siv khoom cov ntaub ntawv.

Peb puas tuaj yeem tsim qhov ntsuas tsis yog pawg ntawm cov kab tsis tshwj xeeb?

Yog li, thaum koj tsim qhov ntsuas qhov ntsuas - nws yuav tsum yog qhov tshwj xeeb. Tab sis, SQL Server tsis xav kom koj tus yuam sij clustering yog tsim rau ntawm ib kab tshwj xeeb. Koj tuaj yeem tsim nws ntawm txhua kab(s) koj xav tau. Internally, yog hais tias tus yuam sij clustering tsis tshwj xeeb ces SQL Server yuav "uniquify" nws los ntawm kev ntxiv ib tug 4-byte integer rau cov ntaub ntawv.

Dab tsi yog qhov tsis sib xws?

Thaum koj tsim ib qho kev txwv UNIQUE, qhov tshwj xeeb tsis suav nrog qhov ntsuas yog tsim los tswj kev txwv UNIQUE los ntawm lub neej ntawdKoj tuaj yeem hais qhia qhov sib txawv tshwj xeeb yog qhov ntsuas ntsuas ntawm lub rooj ua tsis muaj lawm. Yog xav paub ntxiv, mus saib Cov Kev Txwv Tshwj Xeeb thiab Tshawb Xyuas Cov Kev Txwv.

Can clustered index muaj nuj nqis?

Rau qhov ntsuas qhov ntsuas, kab ntawv tsis tas yuav yog qhov tshwj xeeb thiab / lossis tsis muaj null. Ib kem nrog duplicates thiab null qhov tseem ceeb yog qhov zoo rau kev tsim kom muaj kev sib koom ua ke. Rau tus yuam sij txawv teb chaws, nws yuav tsum tau hais txog ib kab nrog cov cim tshwj xeeb ntawm nws tab sis tsis tas yuav yog tus yuam sij tseem ceeb lossis tsis muaj nuj nqis.

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