Dab tsi yog kab virtual hauv Oracle?
Dab tsi yog kab virtual hauv Oracle?

Video: Dab tsi yog kab virtual hauv Oracle?

Video: Dab tsi yog kab virtual hauv Oracle?
Video: khuv xim koj ua dab tsi By Paj vuam vaj nkauj tawm tshiab 2023 2024, Kaum ib hlis
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Taw qhia rau lub Oracle virtual kab

A virtual kab yog ib lub rooj kem uas nws qhov tseem ceeb yog xam tau siv lwm yam kem qhov tseem ceeb, los yog lwm qhov kev txiav txim siab. Yog hais tias koj omit hom ntaub ntawv, lub virtual kab yuav coj cov ntaub ntawv hom ntawm qhov tshwm sim ntawm cov lus qhia.

Kuj nug, dab tsi yog kab virtual hauv SQL?

Hauv kev sib txheeb databases a virtual kab yog lub rooj kem nws tus nqi yog txiav txim siab siv lwm yam kab qhov tseem ceeb, lossis lwm qhov kev txiav txim siab.

Ib yam li ntawd, dab tsi yog kem zais hauv Oracle? Nthuav kab yog kab uas muaj nyob hauv lub rooj tab sis qhov ntawd tsis tuaj yeem xaiv. Muaj ntau yam laj thawj uas Oracle tej zaum yuav tsim ib zais kab -- ob ntawm cov laj thawj ntau dua yog. Thaum a kem yog cim tias tsis siv tab sis tsis poob, nws yog zais cia.

Yog li ntawd, peb puas tuaj yeem tsim qhov ntsuas ntawm kab virtual hauv Oracle?

Virtual kab tuaj yeem siv nyob rau hauv qhov chaw nyob clause ntawm UPDATE thiab DELETE nqe lus tab sis lawv ua tau 'tsis raug hloov kho los ntawm DML. Lawv ua tau siv los ua tus yuam sij muab faib hauv virtual kab raws li partitioning. Indexs tau ua tsim ntawm lawv. Raws li koj tej zaum yuav tau kwv yees, oracle yuav tsim muaj nuj nqi raws li indexes raws li peb tsim ntawm cov rooj qub.

Dab tsi yog tus kheej kem hauv Oracle?

Taw qhia rau Oracle tus kheej kab Cov tus kheej kab yog ib qho tseem ceeb heev rau tus thawj tus yuam sij surrogate kem . Thaum koj ntxig ib kab tshiab rau hauv tus kheej kab , Oracle auto-generates thiab ntxig tus nqi sequential rau hauv kem . Yog koj muab tus nqi, Oracle yuav ntxig tus nqi ntawd rau hauv tus kheej kab.

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