Video: Dab tsi yog qhov ntxig anomaly?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Ib Ntxig Anomaly tshwm sim thaum tej yam ntxwv ua tsis tau ntxig nyob rau hauv lub database tsis muaj lwm yam cwj pwm. Piv txwv li qhov no yog lub converse ntawm delete anomaly - Peb tsis tuaj yeem ntxiv chav kawm tshiab tshwj tsis yog tias peb muaj tsawg kawg yog ib tus tub ntxhais kawm cuv npe hauv chav kawm.
Yog li ntawd, dab tsi yog qhov deletion anomaly?
Deletion Anomaly . A tshem tawm anomaly tshwm sim thaum koj rho tawm cov ntaub ntawv uas tej zaum yuav muaj cov cwj pwm uas yuav tsum tsis txhob muab tshem tawm. Piv txwv li, yog tias peb tshem tawm cov ntaub ntawv hais txog tus lej kawg ntawm ib ceg, xws li tus lej A-101 ntawm ceg hauv plawv nroog hauv daim duab 10.4, tag nrho cov ntaub ntawv ceg yuav ploj mus.
Ib yam li ntawd, 3 qhov tsis txaus ntseeg yog dab tsi? Muaj peb hom ntaub ntawv Kev tsis sib haum xeeb : Hloov tshiab Kev tsis sib haum xeeb , Insertion Kev tsis sib haum xeeb , thiab Deletion Kev tsis sib haum xeeb.
Ntawm no, dab tsi yog qhov txawv txav hauv DBMS?
Cov teeb meem no tshwm sim los ntawm kev sib raug zoo uas tau tsim ncaj qha los ntawm cov neeg siv kev pom yog hu ua anomalies . Muaj peb hom anomalies : hloov tshiab, tshem tawm thiab ntxig anomalies . Kev hloov tshiab anomaly yog cov ntaub ntawv tsis sib xws uas tshwm sim los ntawm cov ntaub ntawv redundancy thiab hloov tshiab ib nrab.
Koj yuav tiv thaiv cov ntaub ntawv anomaly li cas?
Rau tiv thaiv Cov teeb meem no, koj tuaj yeem normalize cov qauv database. Normalization feem ntau entails faib ib lub rooj database rau hauv ob lub rooj yooj yim. Hloov kho anomalies yog li ntawd lub npe vim hais tias lawv yog generated los ntawm qhov sib ntxiv ntawm, hloov mus rau, los yog deletion ntawm cov ntaub ntawv los ntawm lub rooj database.
Pom zoo:
Dab tsi yog qhov ntxig thiab tshem tawm anomalies?
Ib tug deletion anomaly yog qhov tsis xav poob ntawm cov ntaub ntawv vim deletion ntawm lwm cov ntaub ntawv. Insertion anomaly yog qhov tsis muaj peev xwm ntxiv cov ntaub ntawv rau hauv cov ntaub ntawv vim tsis muaj lwm cov ntaub ntawv
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