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