sql - 从单个表中两次选择同一列但条件不同

Question

我想显示员工的姓名和编号以及他们老板的编号和姓名，如下所示:



只有一张 table :



到目前为止我试过这个:

SELECT  
    ID, 
    Name, 
    Boss, 
    (SELECT Name FROM Employees WHERE ID IN (SELECT Boss FROM Employees))
FROM Employees

但它给了我一个错误:

"Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression"

Answer 1

您需要自行加入；就像是:

Select a.ID, a.Name, b.ID as Boss, b.Name as BossName
from Employees A
left join Employees B
on a.Boss = b.ID