• SQL多表联系查询


    SQL多表联系查询

    首先二张表连接查询:A表:EUser  B表:ESchool

    一、外连接:左连接、右连接、全然外连接。

    左连接:left join 或 left outer join

      select * from EUser left join ESchool  on EUser.SchoolId=ESchool.ScholId 

    右连接:right join 或 right outer join

    select * from EUser right join ESchool  on EUser.SchoolId=ESchool.ScholId 

    全然外连接:  full join 或 full outer join

      select * from EUser full join ESchool  on EUser.SchoolId=ESchool.ScholId 

    二、内连接: join 或 inner join

    select * from EUser INNER JOIN ESchool  on EUser.SchoolId=ESchool.ScholId 

    三张表连接查询:A表:EUser  B表:ESchool  C表:EXibu

    方法一:

      select * from EUser INNER JOIN ESchool  on EUser.SchoolId=ESchool.ScholId 
      INNER JOIN EXibu on ESchool.ScholId=EXibu.SchoolId and EUser.DepartmentId=EXibu.DepartmentId

    方法二:

      select * from EUser as sc left join ESchool as s on s.ScholId=sc.SchoolId
      left join EXibu as c on c.DepartmentId=sc.DepartmentId

    了解内连接与外连接可以:https://www.cnblogs.com/mvpbest/p/13879121.html

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  • 原文地址:https://www.cnblogs.com/mvpbest/p/15057401.html
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