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Video: Kuv yuav ua li cas los tsim ib qho kev koom nrog hauv MySQL?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
MySQL INner JOIN
- Ua ntej, qhia cov lus tseem ceeb uas tshwm hauv NTAWM kab lus (t1).
- Thib ob, qhia lub rooj uas yuav koom nrog lub rooj tseem ceeb, uas tshwm nyob rau hauv lub PIB HAIV NEEG clause (t2, t3, …).
- Thib peb, qhia a koom mob tom qab ON lo lus tseem ceeb ntawm lub PIB HAIV NEEG lus.
Ib yam li ntawd, kuv yuav koom nrog MySQL li cas?
Rau koom rooj, koj siv tus ntoo khaub lig koom , sab hauv koom , sab laug koom , los yog txoj cai koom clause rau qhov sib xws ntawm koom . Cov koom clause yog siv nyob rau hauv SELECT nqe lus tshwm sim tom qab FROM clause. Nco ntsoov tias MySQL tsis tau txhawb nqa lub TUB RO Koom tseem.
Ib tug kuj yuav nug, dab tsi yog koom nrog hauv MySQL nrog piv txwv? Kev ua ntawm koom hauv MySQL hais txog smashing ob lossis ntau lub rooj rau hauv ib lub rooj. Koj siv tau JOINS hauv SELECT, UPDATE thiab DELETE cov nqe lus rau koom tus MySQL rooj. Peb yuav pom ib piv txwv ntawm LEFT Koom kuj uas txawv ntawm qhov yooj yim MySQL JOIN.
Ib yam li ntawd, koj ua li cas koom nrog sab hauv?
SQL Server INNER JOIN syntax
- Ua ntej, qhia lub ntsiab lus (T1) hauv NTAWM kab lus.
- Qhov thib ob, qhia cov lus thib ob hauv INNER JOIN clause (T2) thiab kev koom ua ke. Tsuas yog kab uas ua rau kev koom ua ke los ntsuas qhov tseeb yog suav nrog hauv qhov tshwm sim.
Lub luag haujlwm ntawm kev koom nrog sab hauv yog dab tsi?
Lub ntsiab lus ntawm SQL Inner Join Inner Koom clause hauv SQL Server tsim ib lub rooj tshiab (tsis yog lub cev) los ntawm kev sib txuas cov kab uas muaj qhov sib xws hauv ob lossis ntau lub rooj. Qhov no koom yog ua raws li kev sib raug zoo (lossis ib qho kev sib koom ua ke) ntawm cov ntxhuav thiab siv los khaws cov ntaub ntawv uas tshwm hauv ob lub rooj.
Pom zoo:
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