Ib nrab Dependency tshwm sim thaum tus yam ntxwv tsis yog thawj tus cwj pwm ua haujlwm nyob ntawm ib feem ntawm tus neeg sib tw tus yuam sij. Daim Ntawv 2nd Ib txwm (2NF) tshem tawm Ib Feem Kev Cia Siab.
Dab tsi yog qhov kev vam khom ib nrab?
Ib nrab Dependency yog a daim ntawv ntawm Kev Ua Haujlwm Kev vam meej uas tuav ntawm cov yam ntxwv. … Piv txwv li, nyob rau hauv ib tug functional dependency PQ → R, yog P ib leeg los yog Q ib leeg muaj peev xwm cim R, ces qhov no yog hais tias yog ib feem Functional Dependency.
Dab tsi yog qhov normalization kev vam khom?
Ib qho kev ua haujlwm puv ntoob yog xeev ntawm database normalization uas sib npaug rau tus qauv normalization ntawm Thib Ob Hom Ntawv (2NF). Nyob rau hauv luv luv, qhov no txhais tau hais tias nws ua tau raws li qhov yuav tsum tau ntawm First Normal Form (1NF), thiab tag nrho cov yam ntxwv tsis tseem ceeb yog tag nrho functionally nyob ntawm tus yuam sij tseem ceeb.
Dab tsi yog tag nrho thiab ib nrab kev vam khom?
Nyob rau hauv kev ua haujlwm puv ntoob, tsis yog tus cwj pwm tseem ceeb yog ua haujlwm nyob ntawm qhov tus neeg sib tw tus yuam sij. Hauv ib feem ntawm qhov kev vam khom, tsis yog tus cwj pwm tseem ceeb yog ua haujlwm nyob ntawm ib feem ntawm tus neeg sib tw tus yuam sij. … Nyob rau hauv ib feem ntawm kev vam khom, yog tias peb tshem tawm ib qho cwj pwm ntawm X, ces qhov kev vam khom tseem yuav muaj nyob.
Qhov kev vam khom twg yog siv rau hauv normalization?
Ntau Hom Kev Ua Haujlwm Zoo Tshaj Plaws uas siv rau hauv cov txheej txheem Normalization yog: Tag Nrho Kev Cia Siab . Partial Dependency . Txoj kev vam meej.
