在SQL Server中在相同条件下联接两个表

Question

我有两个桌子， cafedetails和employeedetails

• cafedetails具有“ cafemanagerid”和“ staffid”列
• employeedetails具有栏employeeid，employeename

我想获取完整的详细信息

cafemanagerid, name, staffid, name

我的查询：

select 
    cafemanagerid, employeename as cafemanagerName, 
    staffid, employeename as staffname
from 
    cafedetails, employeedetails
where 
    cafemanagerid = employeeid 
    and staffid = employeeid 

我知道不起作用，但是如何实现呢？

帮我..

Answer 1

您需要两次加入employeedetails ，每个都有不同的别名。 在此示例中，我使用一个完整的外部联接来显示数据（如果匹配）。 如果其他不存在，则可能会出现Null。

SELECT 
    cd.cafemanagerid,
    cafe.employeename AS cafemanagerName,
    cd.staffid,
    staf.employeename AS staffname 
FROM 
    cafedetails AS cd
    FULL OUTER JOIN employeedetails AS cafe ON cd.cafemanagerid = cafe.employeeid
    FULL OUTER JOIN employeedetails AS staf ON cd.staffid = staf.employeeid

如果您希望仅在两者都存在的行，则将FULL OUTER JOIN更改为INNER JOIN