Kab thiab kab hu ua dab tsi hauv DBMS?
Kab thiab kab hu ua dab tsi hauv DBMS?

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Video: Kab thiab kab hu ua dab tsi hauv DBMS?
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Hauv computer science terminology, kab qee zaum hu ua "tuples," kab yuav raug xa mus rau "tus cwj pwm," thiab cov rooj lawv tus kheej tej zaum yuav hu ua "kev sib raug zoo." Ib lub rooj tuaj yeem pom tau raws li qhov matrix ntawm kab thiab kab, qhov twg txhua qhov kev sib tshuam ntawm kab thiab kab ntawv muaj cov nqi tshwj xeeb.

Ib sab ntawm no, kab thiab kab hu ua dab tsi hauv cov ntaub ntawv?

Txhua kab hauv a database table sawv cev rau ib qho piv txwv ntawm hom khoom uas tau piav qhia hauv lub rooj ntawd. A kab kuj yog hu ua ib daim ntawv. Cov kab . Cov kab nyob rau hauv ib lub rooj yog cov txheej ntawm qhov tseeb uas peb tau taug qab txog yam khoom ntawd. A kem kuj yog hu ua ib attribute.

kab thiab kab yog dab tsi? Cov kab yog ib qho kev txiav txim uas tib neeg, khoom lossis cov duab muab tso rau ib sab lossis hauv kab ncaj nraim. Kev faib ntsug ntawm qhov tseeb, cov duab lossis lwm yam ntsiab lus raws li qeb, hu ua kem . Kab mus hla, i.e. los ntawm sab laug mus rau sab xis. Ntawm qhov tsis sib xws, Cov kab yog teem los ntawm nce mus rau down.

Ntawm no, peb hu ua kem nyob rau hauv database li cas?

Hauv kev sib raug zoo database , a kem yog ib txheej ntawm cov ntaub ntawv muaj nuj nqis ntawm ib yam yooj yim, ib tug nqi rau txhua kab ntawm cov database . A kem tau kuj be hu ua ib attribute. Txhua kab yuav muab cov ntaub ntawv tus nqi rau txhua tus kem thiab yuav ces yuav to taub raws li ib tug qauv ntaub ntawv tus nqi.

Cov kab hu ua dab tsi?

Lub Sijhawm Teev Taw: Tsev Neeg thiab Lub Sijhawm. Nyob rau hauv lub sij hawm ntawm lub ntsiab lus, muaj xya kab rov tav kab ntawm lub ntsiab hu ua lub sij hawm. Qhov ntsug kab ntawm cov ntsiab lus yog hu ua pab pawg, lossis tsev neeg. Feem ntau txoj kev uas lub sij hawm teem sij hawm yog cais los ntawm hlau, nonmetals, thiab metalloids.

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