sql查詢創建新列並添加數據

Question

我想用他們經理的名字檢索員工姓名。

例如：

Employee_Lastname：WARX
Employee_Firstname：CYNTHIA
MANAGER_NANE：史密斯

Warx Cythnia有經理，Manager_ID = 7369誰是Smith John，因為Smith有Employee_ID = 7369

我想創建MANGER_NAME列並添加數據...

Answer 1

也許你只想投影記錄的價值，而不是通過在表中添加新列？ 你只需加入這個，

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，您不會存儲此類信息。 但是查詢時可以輕松獲取：

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