Koj yuav tsum siv kev ncaj ncees rau kev xa mus?

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Koj yuav tsum siv kev ncaj ncees rau kev xa mus?
Koj yuav tsum siv kev ncaj ncees rau kev xa mus?

Video: Koj yuav tsum siv kev ncaj ncees rau kev xa mus?

Video: Koj yuav tsum siv kev ncaj ncees rau kev xa mus?
Video: peb cov ntseeg yuav tsum tau ncaj ncees 100% pt xyooj 2020 {Audio officail} 2024, Kaum ib hlis
Anonim

Thaum koj tsim kev sib raug zoo ntawm ob lub rooj, feem ntau nws yog ib lub tswv yim zoo los tswj hwm kev ncaj ncees. Kev lees paub ncaj ncees khaws cov ntaub ntawv raugthiab xyuas kom koj tsis txhob yuam kev hloov lossis tshem tawm cov ntaub ntawv cuam tshuam hauv ib lub rooj tab sis tsis nyob hauv lwm qhov.

Kuv puas xav tau kev ntseeg ncaj ncees?

Qhov tseem ceeb ntawm kev ncaj ncees ntawm kev xa musLub tswv yim no yuav tsum nyob hauv peb lub siab ib txwm thaum peb tsim cov qauv ntaub ntawv. Nws yog lub hauv paus ntawm cov ntaub ntawv kev ncaj ncees nyob rau hauv cov ntaub ntawv system. … Tus yuam sij txawv teb chaws ntawm lub rooj siv (cov ntaub ntawv teeb tsa, cov ntaub ntawv chaw) tseem yuav tsum tau xa mus rau kab siv tau hauv thiab cov lus hais.

Dab tsi yog qhov teeb meem nrog kev ncaj ncees?

Raws li cov ntsiab lus yooj yim, 'kev ntseeg ncaj ncees' lav tias lub hom phiaj 'xa mus' yuav raug pom. Qhov tsis muaj kev ncaj ncees ntawm kev xa mus rau hauv cov ntaub ntawv tuaj yeem ua rau cov ntaub ntawv sib raug zoo kom rov qab cov ntaub ntawv tsis tiav, feem ntau tsis muaj qhov qhia txog qhov yuam kev.

Vim li cas kev ncaj ncees xa mus rau hauv database?

Referential integrity (RI) yog ib lo lus siv nrog cov ntaub ntawv sib raug zoo los piav txog kev ncaj ncees ntawm kev lag luam kev sib raug zoo uas sawv cev rau hauv schema. Nws kom ntseeg tau tias kev sib raug zoo ntawm cov rooj nyob sib xws.

Ib qho piv txwv ntawm kev hais ncaj ncees yog dab tsi?

Kev ncaj ncees hais kom tus yuam sij txawv teb chaws yuav tsum muaj tus yuam sij tseem ceeb sib xws lossis nws yuav tsum yog null. … Piv txwv ntawm kev txwv kev ncaj ncees nyob rau hauv Cov Neeg Siv Khoom / Kev Txiav Txim database ntawm Lub Tuam Txhab: Customer(CustID, CustName) Order(OrderID, CustID, OrderDate)

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