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0005_连接 #12

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songshua295 opened this issue Apr 26, 2023 · 0 comments

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songshua295 commented Apr 26, 2023

https://ob.tianzhongs.ml/0005_%E8%BF%9E%E6%8E%A5

0005_连接根据连接方式来分类内连接：inner join xxx on 条件等值连接非等值连接自连接：通过自己来建立连接外连接： left/right outer join xxx on 条件：主表的所有不满足条件的也会显示出来左外连接（左连接）示例： left outer join xxx on 条件 outer可以省略右外连接（右连接）示例示例：多张表连接查询全连接（这个不讲，很少用！）

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