Video: Txhua lub rooj yuav tsum muaj tus yuam sij tseem ceeb?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Txhua lub rooj ua tau muaj (tab sis ua tsis yog muaj rau muaj) qhov tseem ceeb . Cov kab los yog kab lus txhais raws li tus thawj tus yuam sij xyuas kom uniqueness nyob rau hauv lub rooj ; tsis muaj ob kab ua tau muaj tib yam tus yuam sij . Cov thawj tus yuam sij ntawm ib rooj kuj tseem yuav pab txheeb xyuas cov ntaub ntawv hauv lwm yam rooj , thiab ua ib feem ntawm qhov thib ob lub rooj tseem ceeb.
Ntxiv mus, txhua lub rooj yuav tsum muaj lub ntsiab tseem ceeb?
Txhua lub rooj nyob rau hauv ib tug relational database yuav tsum muaj qhov tseem ceeb . Cov thawj tus yuam sij yog ib kem, los yog kab ke, uas tso cai rau txhua kab hauv lub rooj kom paub qhov txawv. Tsis muaj ob kab hauv ib rooj nrog a thawj tus yuam sij ua tau muaj tib yam thawj tus yuam sij tus nqi.
Tsis tas li ntawd, puas yog Primary Key yuam hauv SQL? Koj tuaj yeem siv UNIQUE (kev txwv tsis yog qhov ntsuas) thiab TSIS TXHOB ua ke los tswj hwm yuam sij hauv SQL ntawv . Yog li ntawd, tsis yog, a thawj tus yuam sij (los yog TSEEM CEEB ) tsis tsim nyog nyob rau hauv SQL ntawv Server.
Raws li txoj cai, peb puas tuaj yeem muaj rooj tsis muaj tus yuam sij tseem ceeb?
Tsis yog. Txhua rooj yuav tsum muaj qee kem (los yog cov kab ke) uas qhia txog ib qho thiab tsuas yog ib kab xwb. Nws ua rau nws yooj yim dua los tswj cov ntaub ntawv. Nws muaj tseeb, tsis muaj a thawj tus yuam sij (los yog qee qhov tshwj xeeb tus yuam sij ), koj tsis txhob muaj ib qho kev ntxig anomaly yog tias koj mus rau ntxig tib cov ntaub ntawv ntau zaus.
Yuav muaj pes tsawg tus yuam sij tseem ceeb hauv lub rooj?
ib qho tseem ceeb
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
Dab tsi yog tus yuam sij ntiag tug thiab pej xeem tus yuam sij hauv Blockchain?
Thaum ib tug neeg xa koj cryptocoins hla Blockchain, lawv tau xa lawv mus rau qhov hashed version ntawm qhov hu ua "Public Key". Muaj lwm tus yuam sij uas zais ntawm lawv, uas yog hu ua "Private Key." Qhov Private Key no yog siv los muab Public Key
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