Video: Dab tsi yog qhov tseem ceeb hauv lub database?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
A thawj tus yuam sij yog kev sib txheeb tshwj xeeb database kab lus (los yog kev sib xyaw ntawm kab) tsim los txheeb xyuas tag nrho cov ntaub ntawv teev tseg. A tus tseem ceeb Cov yam ntxwv tseem ceeb yog: Nws yuav tsum muaj tus nqi tshwj xeeb rau txhua kab ntawm cov ntaub ntawv. Nws tsis tuaj yeem muaj cov nqi null.
Ua raws li qhov xav tau, qhov tseem ceeb thiab qhov piv txwv yog dab tsi?
A thawj tus yuam sij yog ib kab lus uas twb muaj lawm los yog ib kem uas tshwj xeeb tsim los ntawm cov ntaub ntawv raws li cov lus teev tseg. Rau piv txwv , cov tub ntxhais kawm raug muab tus lej cim tshwj xeeb (ID) ib txwm muaj, thiab txhua tus neeg laus tau txais cov lej tseem ceeb ntawm tsoomfwv thiab tshwj xeeb-tus lej Social Security.
Ib yam li ntawd, tus yuam sij tseem ceeb thiab txawv teb chaws yog dab tsi hauv database? Thawj tus yuam sij tshwj xeeb txheeb xyuas cov ntaub ntawv hauv lub rooj. Tus yuam sij txawv teb chaws yog ib daim teb nyob rau hauv lub rooj uas yog thawj tus yuam sij nyob rau hauv lwm lub rooj. Los ntawm lub neej ntawd, Thawj tus yuam sij yog clustered index thiab cov ntaub ntawv nyob rau hauv lub database lub rooj yog lub cev lub cev nyob rau hauv cov kab ke ntawm pawg index.
Hauv qhov no, dab tsi yog qhov tseem ceeb hauv database muab piv txwv?
A thawj tus yuam sij , kuj hu a thawj keyword, yog a tus yuam sij hauv kev sib raug zoo database uas yog tshwj xeeb rau txhua cov ntaub ntawv. Nws yog tus cim tshwj xeeb, xws li tus lej tsav tsheb, tus lej xov tooj (nrog rau thaj chaw code), lossis tus lej cim tsheb (VIN). Kev sib raug zoo database yuav tsum muaj ib txwm muaj ib thiab xwb ib qho tseem ceeb.
Dab tsi yog qhov tseem ceeb sib xyaw hauv cov ntaub ntawv?
Hauv database tsim, a yuam sij ua ke yog tus neeg sib tw tus yuam sij uas muaj ob lossis ntau tus cwj pwm (cov kab lus) uas ua ke tshwj xeeb txheeb xyuas qhov xwm txheej tshwm sim (cov kab lus). A key sib xyaw yog a yuam sij ua ke uas txhua tus cwj pwm uas ua rau lub tus yuam sij yog ib qho yooj yim (txawv teb chaws) tus yuam sij nyob rau hauv nws tus kheej txoj cai.
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