Video: Tus nqi atomic yog dab tsi?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Ib atomic nqi yog a tus nqi uas faib tsis tau. Piv txwv li, hauv cov lus qhia hauv qab no, tus tus nqi nyob rau hauv [Xim] kab hauv thawj kab tuaj yeem muab faib ua "liab" thiab "ntsuab", yog li [TABLE_PRODUCT] tsis nyob hauv 1NF. Ib pawg rov ua dua txhais tau hais tias ib lub rooj muaj ob lossis ntau kab uas muaj feem cuam tshuam.
Yog li ntawd, Atomic txhais li cas hauv database?
Atomicity ( database systems) ib atomic kev hloov pauv yog ib qho kev sib cais tsis tau thiab tsis tuaj yeem tshwm sim database kev ua haujlwm xws li txhua yam tshwm sim, lossis tsis muaj dab tsi tshwm sim. Kev lees paub ntawm atomicity tiv thaiv kev hloov tshiab rau cov database tshwm sim tsuas yog ib feem, uas ua tau ua rau muaj teeb meem ntau dua li tsis lees paub tag nrho cov koob tawm.
Tsis tas li ntawd, piv txwv li 1nf yog dab tsi? First normal form ( 1 NF ) Raws li txoj cai ntawm thawj daim ntawv ib txwm, tus cwj pwm (kem) ntawm lub rooj tsis tuaj yeem tuav ntau yam nqi. Nws yuav tsum tuav tsuas yog atomic nqi. Piv txwv : Piv txwv tias ib lub tuam txhab xav khaws cov npe thiab cov ntaub ntawv tiv tauj ntawm nws cov neeg ua haujlwm. Nws tsim ib lub rooj uas zoo li no: emp_id.
Hauv qhov no, 1nf txhais li cas?
Thawj daim ntawv qub
Dab tsi yog cov ntaub ntawv tsis yog atomic?
Tsis yog - atomic Hom. Tus nqi ntawm cov ntaub ntawv atomic hom tsis tuaj yeem muab faib ntxiv. Nws tuaj yeem yog qhov qub lossis muab tau zoo li cov hlua, cov lej, lej, lej, hnub thiab lwm yam. Qhov tseem ceeb ntawm cov ntaub ntawv atomic hom tsis tuaj yeem muab faib ntxiv. Nws tuaj yeem yog qhov qub lossis muab tau zoo li cov hlua, cov lej, lej, hnub tim thiab lwm yam.
Pom zoo:
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