如何在同一查询中多次引用单个表？

Question

有时我需要将同一个表视为两个单独的表.解决办法是什么？

Answer 1

您可以参考,只需确保使用表别名

select a.EmployeeName,b.EmployeeName as Manager
from Employees A
join Employees B on a.Mgr_id=B.Id

Answer 2

在SQL中使用类似变量名的别名:

select
    A.Id,
    A.Name,
    B.Id as SpouseId,
    B.Name as SpouseName
from
    People A
    join People B on A.Spouse = B.id