Table yog nyob rau hauv 1NF (Thawj ib txwm daim ntawv) Tsis muaj tus cwj pwm tsis zoo yog nyob ntawm qhov tsim nyog ntawm cov neeg sib tw tus yuam sij ntawm lub rooj.
Daim ntawv twg ib txwm yog tus neeg siv khoom yog tias nws muaj cov yam ntxwv hauv qab no?
Kev piav qhia: Thawj daim ntawv ib txwm siv los tshem tawm cov ntaub ntawv sib tshooj. Nqe lus piav qhia: Ib lub rooj nyob hauv 4NF yog thiab tsuas yog, rau txhua qhov ntawm nws qhov tsis tseem ceeb ntau qhov kev vam khom X \twoheadrightarrow Y, X yog superkey-uas yog, X yog tus neeg sib tw yuam sij los yog superset ntawm no.
1NF 2NF 3NF thiab BCNF yog dab tsi?
1NF (First Normal Form) 2NF (Form Thib Ob) 3NF (Third Normal Form) BCNF (Boyce-Codd Normal Form) 4NF (Fourth Normal Form)
2nd ib txwm daim ntawv nrog piv txwv yog dab tsi?
Kauj Ruam thib ob hauv Kev Ua Raws Cai yog 2NF. Ib lub rooj yog nyob rau hauv 2NF, tsuas yog hais tias ib tug kev sib raug zoo nyob rau hauv 1NF thiab ua tau raws li tag nrho cov kev cai, thiab txhua txhua tus cwj pwm tsis tseem ceeb yog tag nrho nyob ntawm tus yuam sij tseem ceeb. Daim Ntawv Foos Thib Ob no tshem tawm ib feem ntawm kev vam khom rau cov yuam sij tseem ceeb.
1st 2nd thiab 3rd daim ntawv ib txwm piav qhia nrog piv txwv yog dab tsi?
Ib qho kev sib raug zoo yog nyob rau hauv daim ntawv thib ob yog tias nws nyob hauv 1NF thiab txhua tus cwj pwm tsis tseem ceeb yog qhov ua haujlwm tau zoo nyob ntawm qhov tseem ceeb. … Ib qho kev sib raug zoo yog nyob rau hauv peb daim ntawv ib txwm yog nws nyob hauv 2NF thiab tsis muaj kev vam khom ntawm cov yam ntxwv tsis tseem ceeb. (piv txwv li 2NF + tsis muaj kev hloov pauv hloov pauv).
