SQL多表聯絡查詢

首先二張表連線查詢：A表：EUser B表：ESchool

一、外連線：左連線、右連線、全然外連線。

左連線：left join 或 left outer join

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

右連線：right join 或 right outer join

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

全然外連線： full join 或 full outer join

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

二、內連線：join或 inner join

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

三張表連線查詢：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

瞭解內連線與外連線可以：https://www.cnblogs.com/mvpbest/p/13879121.html