sql join中on條件后接and和where

目錄

場景1：left join + on a.xx = b.xx and a.xx2 = 'aa'

場景2：left join + on a.xx = b.xx and b.xx2 = 'aa'

場景3：left join + on a.xx = b.xx where b.xx2 = 'aa'

場景4：inner join + on a.xx = b.xx where a.xx2 = 'aa'

場景5：inner join + on a.xx = b.xx and  a.xx2 = 'aa'

場景6：inner join + on a.xx = b.xx  and  b.xx2 = 'aa'

總結

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場景1：left join + on a.xx = b.xx and a.xx2 = 'aa'

場景2：left join + on a.xx = b.xx and b.xx2 = 'aa'

場景3：left join + on a.xx = b.xx where b.xx2 = 'aa'

場景4：inner join + on a.xx = b.xx where a.xx2 = 'aa'

場景5：inner join + on a.xx = b.xx and  a.xx2 = 'aa'

場景6：inner join + on a.xx = b.xx  and  b.xx2 = 'aa'

總結

1、where 條件可以理解為，關聯后，數據作為一個整體的過濾條件

2、on 后面的and 條件為關聯條件，如果是left join，則不對主表記錄行數產生影響；如果是inner join則，效果等同於where條件