Cov txheej txheem:
Video: Yuav ua li cas koj teev tus yuam sij tseem ceeb hauv SQL lus nug?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Siv SQL Server Management Studio
- Hauv Object Explorer, right-click lub rooj uas koj xav ntxiv qhov tshwj xeeb txwv, thiab nyem Tsim.
- Hauv Table Designer, nyem kab xaiv rau kab ntawv database koj xav kom txhais raws li qhov thawj tus yuam sij .
- Right-click tus kab xaiv rau kab thiab xaiv Set Primary Key .
Dhau li ntawd, dab tsi yog qhov tseem ceeb hauv SQL nrog piv txwv?
Tus yuam sij tseem ceeb yog qhov chaw hauv a rooj uas tshwj xeeb txheeb xyuas txhua kab / cov ntaub ntawv hauv cov ntaub ntawv rooj . Cov yuam sij tseem ceeb yuav tsum muaj cov txiaj ntsig tshwj xeeb. Ib kab ntawv tseem ceeb tsis tuaj yeem muaj NULL qhov tseem ceeb. A rooj tuaj yeem muaj tsuas yog ib qho tseem ceeb, uas yuav muaj xws li ib qho lossis ntau qhov chaw.
Tsis tas li ntawd, tus yuam sij txawv teb chaws hauv DBMS yog dab tsi? A txawv teb chaws key yog ib kem lossis pab pawg kab hauv cov rooj sib tham database uas muab kev sib txuas ntawm cov ntaub ntawv hauv ob lub rooj. Lub tswvyim ntawm referential kev ncaj ncees yog muab los ntawm txawv teb chaws key kev xav. Cov yuam sij txawv teb chaws thiab lawv qhov kev siv yog qhov nyuaj tshaj qhov tseem ceeb cov yuam sij.
Kuj Paub, ua li cas koj ntxiv tus yuam sij tseem ceeb?
Tus yuam sij tseem ceeb tuaj yeem txhais tau hauv CREATE TABLE nqe lus lossis ALTER TABLE nqe lus
- Tsim Cov Ntsiab Tseem Ceeb - Siv CREATE TABLE nqe lus.
- Tsim Cov Ntsiab Tseem Ceeb - Siv ALTER TABLE nqe lus.
- Tso Primary Key.
- Disable Primary Key.
- Qhib Cov Ntsiab Tseem Ceeb.
Tus yuam sij txawv teb chaws tuaj yeem ua tsis tau?
A txawv teb chaws key muaj null qhov tseem ceeb tsis tuaj yeem phim qhov txiaj ntsig ntawm niam txiv tus yuam sij , txij li niam txiv tus yuam sij los ntawm txhais ua tau tsis muaj null tus nqi. Txawm li cas los xij, a null txawv teb chaws key tus nqi yeej ib txwm siv tau, tsis hais tus nqi ntawm ib qho ntawm nws tsis yog- null ntu. Ib lub rooj ua tau muaj ntau cov yuam sij txawv teb chaws.
Pom zoo:
Ib tus yuam sij tseem ceeb puas tuaj yeem muaj ob tus yuam sij txawv teb chaws?
Nws yog qhov zoo kawg nkaus kom muaj ob kab ntawv tseem ceeb txawv teb chaws xa mus rau tib lub ntsiab lus tseem ceeb hauv ib lub rooj sib txawv vim tias txhua tus nqi tseem ceeb txawv teb chaws yuav siv cov ntaub ntawv sib txawv hauv cov lus hais
Koj txhais li cas los ntawm tus yuam sij ntiag tug thiab pej xeem tus yuam sij cryptography?
Nyob rau hauv pej xeem tus yuam sij cryptography, ob tus yuam sij yog siv, ib tug yuam sij yog siv rau encryption thiab thaum lwm yam yog siv rau decryption. 3. Nyob rau hauv private keycryptography, tus yuam sij yog khaws cia tsis pub leejtwg paub. Nyob rau hauv pej xeem tus yuam sij cryptography, ib qho ntawm ob tus yuam sij yog khaws cia tsis pub leejtwg paub
Cov yuam sij tseem ceeb thiab cov yuam sij txawv teb chaws yog dab tsi?
Relation of Primary Key vs Foreign Key Ib lub ntsiab tseem ceeb tshwj xeeb qhia cov ntaub ntawv nyob rau hauv lub rooj sib tham database, whereas tus yuam sij txawv teb chaws yog hais txog lub teb nyob rau hauv ib lub rooj uas yog lub ntsiab tseem ceeb ntawm lwm lub rooj
Puas yog tus yuam sij tseem ceeb kuj yog tus yuam sij txawv teb chaws?
Cov yuam sij tseem ceeb ib txwm yuav tsum muaj qhov tshwj xeeb, cov yuam sij txawv teb chaws yuav tsum tso cai rau qhov tsis muaj txiaj ntsig yog tias lub rooj yog ib qho kev sib raug zoo. Nws yog qhov zoo kawg nkaus siv tus yuam sij txawv teb chaws los ua tus yuam sij tseem ceeb yog tias lub rooj sib txuas los ntawm kev sib raug zoo ib leeg, tsis yog ib qho kev sib raug zoo
Tus yuam sij tseem ceeb thib ob thiab tus yuam sij txawv teb chaws yog dab tsi?
Txawv Teb Chaws Tseem Ceeb: Yog Lub Ntsiab Tseem Ceeb ib lub rooj tshwm (hloov-hais) hauv lwm lub rooj. Secondary (los yog lwm txoj kev) Key: Puas yog ib qho chaw hauv lub rooj uas tsis raug xaiv los ua ib qho ntawm ob hom saum toj no