Database Consistency States Xwb Cov Ntaub Ntawv Muaj Tsuas Siv Tau Tswv Yim Rau Database
Database Consistency hais tias tsuas siv tau cov ntaub ntawv yuav muab sau rau hauv cov ntaub ntawv. Yog hais tias tus lag luam raug sau tseg tias ua txhaum txoj cai tswj hwm cov kev cai, tag nrho cov lag luam yuav muab dov rov qab thiab cov database yuav rov qab mus rau nws lub xeev qub. Ntawm qhov tod tes, yog ib qho lag luam ua tiav executes, nws yuav siv lub database los ntawm ib lub xeev uas ua raws li cov cai rau lwm lub xeev uas tseem ua raws li cov cai.
Database sib npaug tsis txhais tau hais tias qhov kev sib pauv yog lawm, tsuas yog qhov kev sib hloov tsis ua txhaum cov cai uas tau hais tseg los ntawm qhov kev zov me nyuam. Database taub yog ib qho tseem ceeb vim nws tswj cov ntaub ntawv uas tau los hauv thiab tawm tsam cov ntaub ntawv uas tsis haum rau cov cai.
Piv txwv ntawm kev cai sib luag ntawm txoj haujlwm
Piv txwv, ib kem hauv cov ntaub ntawv tsuas muaj qhov tseem ceeb rau cov nyiaj npib li "hau" lossis "tails." Yog hais tias tus neeg siv yuav tsum tau sim muab tso rau hauv "kev sib tw," kev cai tswj hwm rau cov ntaub ntawv database tsis pub nws.
Tej zaum koj yuav muaj kev paub txog cov cai tswj kev tawm ntawm kev tawm hauv ib daim teb hauv daim nplooj ntawv web page. Thaum ib tug neeg sau daim ntawv online thiab tsis nco qab sau rau hauv ib qho ntawm cov chaw uas yuav tsum tau muaj, tus nqi NULL mus rau qhov chaw khaws ntaub ntawv, ua rau daim ntawv tso npe tawm kom mus txog rau ntawm qhov chaw seem dawb.
Kev ua zoo yog qhov theem ob ntawm ACID qauv (Atomicity, Consistency, Isolation, Durability), uas yog ib co txheej txheem rau kev ua kom muaj tseeb ntawm cov ntaub ntawv database.