Video: Puas yog cov yuam sij txawv teb chaws indexed MySQL?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
MySQL xav tau indexes ntawm cov yuam sij txawv teb chaws thiab hais txog yuam sij yog li ntawd txawv teb chaws Cov kev kuaj xyuas tseem ceeb tuaj yeem ceev ceev thiab tsis xav tau lub rooj scan. Xws li ib qhov ntsuas yog tsim nyob rau hauv lub referencing rooj cia li yog hais tias nws tsis muaj nyob.
Ib yam li ib tug yuav nug, yog cov yuam sij txawv teb chaws indexed?
3 Teb. SQL Server yuav tsis cia li tsim ib qho qhov ntsuas ntawm a txawv teb chaws tus yuam sij. A FOREIGN KEY constraint tsis tas yuav txuas mus rau PRIMARY nkaus xwb KEY txwv nyob rau hauv lwm lub rooj; Nws kuj tseem tuaj yeem txhais tau los siv cov kab ntawm UNIQUE txwv hauv lwm lub rooj.
Tsis tas li, kuv yuav nrhiav tau tus yuam sij txawv teb chaws hauv MySQL li cas? pom txawv teb chaws key kev sib raug zoo ntawm lub rooj: Xaiv TABLE_NAME, COLUMN_NAME, CONSTRAINT_NAME, REFERENCED_TABLE_NAME, REFERENCED_COLUMN_NAME NTAWM INFORMATION_SCHEMA. KEY_COLUMN_USAGE WHERE REFERENCED_TABLE_SCHEMA = 'db_name' THIAB REFERENCED_TABLE_NAME = 'table_name';
Yog li ntawd, MySQL puas txhawb cov yuam sij txawv teb chaws?
MySQL txhawb cov yuam sij txawv teb chaws , uas tso cai hla cov ntaub ntawv muaj feem cuam tshuam hla cov rooj, thiab txawv teb chaws tseem ceeb txwv , uas pab khaws cov ntaub ntawv sib xws.
Puas yog cov yuam sij txawv teb chaws indexed Postgres?
6 Teb. PostgreSQL yuav tsim indexes ntawm thawj yuam sij thiab cov kev txwv tshwj xeeb, tab sis tsis yog nyob rau ntawm kev xa tawm ntawm txawv teb chaws kev sib raug zoo tseem ceeb. Yog li, nws tsis tsim nyog los tsim ib qho qhov ntsuas meej meej rau cov kab ntawv 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
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
Ib tus yuam sij txawv teb chaws puas tuaj yeem siv lwm tus yuam sij txawv teb chaws?
1 Teb. Tus yuam sij txawv teb chaws tuaj yeem siv txhua qhov chaw uas txhais tau tias nws txawv. Yog hais tias qhov tshwj xeeb teb yog nws tus kheej txhais tau tias yog tus yuam sij txawv teb chaws, nws tsis txawv. Yog tias nws yog thaj chaw tshwj xeeb, nws kuj tuaj yeem yog lub hom phiaj ntawm lwm FK
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