sql查询创建新列并添加数据

Question

我想用他们经理的名字检索员工姓名。

例如：

Employee_Lastname：WARX
Employee_Firstname：CYNTHIA
MANAGER_NANE：史密斯

Warx Cythnia有经理，Manager_ID = 7369谁是Smith John，因为Smith有Employee_ID = 7369

我想创建MANGER_NAME列并添加数据...

Answer 1

也许你只想投影记录的价值，而不是通过在表中添加新列？ 你只需加入这个，

SELECT  a.*,
        b.Employee_LastName AS MANAGER_LASTNAME
FROM    EmpTable a
        LEFT JOIN EmpTable b
            ON a.Manager_ID = b.Employee_ID

要么

SELECT  a.Employee_LastName,
        a.Employee_FirstName,
        b.Employee_LastName AS MANAGER_LASTNAME
FROM    EmpTable a
        LEFT JOIN EmpTable b
            ON a.Manager_ID = b.Employee_ID

Answer 2

通常，您不会存储此类信息。 但是查询时可以轻松获取：

select
   t1.Employee_Lastname,
   t1.Employee_Firstname,
   t2.Employee_Lastname as manager_name
from [table] t1
       left join
     [table] t2
        on
           t1.manager_id = t2.employee_id