Cov txheej txheem:
- Yuav ua li cas yog tus yuam sij tseem ceeb tsis txawv?
- Vim li cas tag nrho cov ntsiab lus tseem ceeb yuav tsum yog qhov tshwj xeeb?
- Puas yog tus yuam sij tseem ceeb yuav tsum muaj qhov tshwj xeeb?
- Puas yog tus yuam sij tseem ceeb tsis yog qhov txawv?
Video: Yuav tsum yog tus yuam sij tseem ceeb yog qhov tshwj xeeb?
2024 Tus sau: Fiona Howard | [email protected]. Kawg hloov kho: 2024-01-10 06:38
Tus yuam sij tseem ceeb yuav tsum yog qhov tshwj xeeb. Tus yuam sij tshwj xeeb tsis tas yuav yog tus yuam sij tseem ceeb - saib tus neeg sib tw tus yuam sij. Qhov ntawd yog, tej zaum yuav muaj ntau tshaj ib qho kev sib txuas ntawm kab ntawm ib lub rooj uas tuaj yeem txheeb xyuas ib kab - tsuas yog ib qho ntawm cov no tuaj yeem xaiv los ua tus yuam sij tseem ceeb.
Yuav ua li cas yog tus yuam sij tseem ceeb tsis txawv?
Txawm tias thaum lub ntsiab_key tau txhais nyob rau hauv txhua qhov kev pom (thiab txhua qhov yog qhov tseeb tshwj xeeb), koj tuaj yeem pom qhov tsis muaj nqi tshwj xeeb / qhov yuam kev tseem ceeb thaum khiav cov lus nug. Qhov no tuaj yeem tshwm sim thaum muaj ntau yam one_to_many koom nrog hauv Kev Tshawb Fawb thiab muaj qhov ntsuas uas sib sau ua ke ntawm cov txiaj ntsig los ntawm ob lossis ntau lub rooj sib txawv
Vim li cas tag nrho cov ntsiab lus tseem ceeb yuav tsum yog qhov tshwj xeeb?
Primary key ncig kev ncaj ncees rau lub rooj. … Ib lub rooj tuaj yeem muaj ntau dua ib tus yuam sij tshwj xeeb tsis zoo li tus yuam sij tseem ceeb. Cov kev txwv tseem ceeb tshwj xeeb tuaj yeem lees txais tsuas yog ib qho NULL tus nqi rau kab. Cov kev txwv tshwj xeeb kuj tau hais los ntawm tus yuam sij txawv teb chaws ntawm lwm lub rooj.
Puas yog tus yuam sij tseem ceeb yuav tsum muaj qhov tshwj xeeb?
A tus yuam sij tseem ceeb yuav tsum yog tus cim. Tus yuam sij tshwj xeeb tsis tas yuav yog tus yuam sij tseem ceeb - saib tus neeg sib tw tus yuam sij. Qhov ntawd yog, tej zaum yuav muaj ntau tshaj ib qho kev sib txuas ntawm kab ntawm ib lub rooj uas tuaj yeem txheeb xyuas ib kab - tsuas yog ib qho ntawm cov no tuaj yeem xaiv los ua tus yuam sij tseem ceeb.
Puas yog tus yuam sij tseem ceeb tsis yog qhov txawv?
Cov yuam sij tseem ceeb tsis tas yuav tshwj xeeb los ntawm kev txhais (txawm tias lawv nyob hauv MySQL). Muaj cov txheej txheem database uas tso cai rau "cov yuam sij tsis tseem ceeb", vim tias lawv tswj hwm lawv tus kheej, feem ntau muab zais, "primary key" hauv "Low ID ".
Pom zoo:
Puas yog tshwj xeeb lossis tshwj xeeb?
Cov lus no muaj lub ntsiab lus zoo ib yam. Qhov txawv tsuas yog nyob rau hauv lawv cov ntawv sau. Kev tshwj xeeb yog nyob deb ntawm qhov kev xaiv nrov dua hauv Asmeskas Lus Askiv, yog li koj yuav tsum siv nws tshwj xeeb nrog cov neeg Asmeskas.
Kuv yuav tsum siv cov lus qhia ua tus yuam sij tseem ceeb?
GUIDs yuav zoo li yog qhov kev xaiv ntuj rau koj tus yuam sij tseem ceeb - thiab yog tias koj xav tau tiag tiag, koj tuaj yeem sib cav siv nws rau PRIMARY KEY ntawm lub rooj. Qhov kuv xav kom tsis txhob ua yog siv GUID kem ua tus yuam sij clustering, uas SQL Server ua los ntawm lub neej ntawd, tshwj tsis yog koj qhia tshwj xeeb tias nws tsis ua .
Vim li cas tus yuam sij tseem ceeb hauv dbms?
Ib tus yuam sij tseem ceeb yog qhov tshwj xeeb kev sib raug zoo ntawm cov rooj sib tham (lossis kev sib txuas ntawm txhua kab) tsim los txheeb xyuas txhua lub rooj cov ntaub ntawvTus yuam sij tseem ceeb yog siv los ua tus cim tshwj xeeb kom nrawm nrawm cov ntaub ntawv hauv lub rooj.
Vim li cas qhov tseem ceeb yog qhov tseem ceeb?
Nws yuav tsum muaj lub zog lub cev thiab lub siab lub ntsws. Qhov tseem ceeb yog qhov tseem ceeb uas tso cai rau koj mus txuas ntxiv thiab ua lub neej zoo. Hauv qhov tseem ceeb, qhov tseem ceeb txhais tau hais tias muaj zog, noj qab nyob zoo, thiab muaj txiaj ntsig zoo.
Tus yuam sij twg yuav tsum tau hu nkauj baritone?
Lub baritone yog nruab nrab ntawm cov txiv neej thiab yog cov txiv neej feem ntau hu nkauj ntau. Raws li nws tsis suav nrog cov yuam sij siab lossis qis heev hauv nws qhov ntau, nws yog qhov yooj yim tshaj rau cov txiv neej hu nkauj. Qhov ntau yam rau tus neeg hu nkauj baritone yog los ntawm G2 rau E4 .
