Video: ERM yog dab tsi hauv database?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Ib qho chaw-kev sib raug zoo qauv ( ERM ) yog ib txoj kev theoretical thiab lub tswv yim ntawm kev qhia cov ntaub ntawv kev sib raug zoo hauv kev tsim kho software. ERM yog a database Cov txheej txheem ua qauv uas tsim cov duab kos duab lossis pom kev sawv cev ntawm lub kaw lus cov ntaub ntawv uas tuaj yeem pab tsim kev sib raug zoo database.
Hauv qhov no, Entity piv txwv yog dab tsi?
npe. The definition of ib qhov chaw yog ib yam uas muaj nyob ntawm nws tus kheej. Ib piv txwv ntawm qhov chaw yog ib lub xeev los yog lub xeev uas tawg mus rau lwm lub teb chaws.
Qhov thib ob, dab tsi yog crow foot notation nyob rau hauv ib tug database? Crow's foot notation Crow's ko taw Cov duab kos sawv cev rau cov koom haum ua lub thawv, thiab kev sib raug zoo raws li kab ntawm cov thawv. Cov duab sib txawv ntawm qhov kawg ntawm cov kab no sawv cev rau tus txheeb ze cardinality ntawm kev sib raug zoo. Crow's foot notation tau siv nyob rau hauv kev tawm tswv yim xyaum CACI.
Ntawm no, ER qauv piav qhia nrog piv txwv li cas?
Lub Koom Haum Kev Sib Raug Zoo Modeling ( ER qauv ) yog graphical mus kom ze rau database design. Nws siv Qhov chaw / Kev sib raug zoo los sawv cev rau cov khoom ntiaj teb tiag. Rau piv txwv txhua tus neeg ua haujlwm ntawm ib lub koom haum yog ib lub koom haum cais. Hauv qab no yog qee cov yam ntxwv tseem ceeb ntawm cov koom haum. Ib lub koom haum muaj ib txheej ntawm cov khoom.
ERD yog dab tsi hauv database?
Ib Daim duab qhia txog kev sib raug zoo ( ERD ) yog ib tug snapshot ntawm cov ntaub ntawv qauv. Ib Daim duab qhia txog kev sib raug zoo qhia cov koom haum (cov rooj) hauv a database thiab kev sib raug zoo ntawm cov rooj hauv qhov ntawd database . Muaj peb yam tseem ceeb hauv ER-Diagrams: Cov chaw yog "cov khoom" uas peb xav khaws cov ntaub ntawv.
Pom zoo:
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