如何在SQL查询中显示employee表中的管理器名称？

Question

我有一个员工表,显示员工编号,姓名和经理的员工编号.我正在尝试创建一个显示emp名称,emp#,manager name和mgr#的查询.

该表如下所示:

EMPNO ENAME  JOB       MGR  HIREDATE  SAL COMM DEPTNO 
7839  KING   PRESIDENT -    17-NOV-81 5000 -   10 
7698  BLAKE  MANAGER   7839 01-MAY-81 2850 -   30 
7782  CLARK  MANAGER   7839 09-JUN-81 2450 -   10 
7566  JONES  MANAGER   7839 02-APR-81 2975 -   20 
7654  MARTIN SALESMAN  7698 28-SEP-81 1250 1400 30 
7499  ALLEN  SALESMAN  7698 20-FEB-81 1600 300 30 
7844  TURNER SALESMAN  7698 08-SEP-81 1500 0   30 
7900  JAMES  CLERK     7698 03-DEC-81 950  -   30 
7521  WARD   SALESMAN  7698 22-FEB-81 1250 500 30 
7902  FORD   ANALYST   7566 03-DEC-81 3000 -   20 

其中三列非常简单,因为它们在表中,但是当我拥有的是经理的员工编号时,我如何添加经理名称？

这是我到目前为止只显示3列的内容

select ename as "Employee", empno as "Emp#", mgr as "Mgr#"  from emp;

任何帮助,将不胜感激

Answer 1

select 
  emp.ename as "Employee", 
  emp.empno as "Emp#", 
  emp.mgr as "Mgr#",
  m.ename as "Manager"
from 
 emp
  LEFT OUTER JOIN emp m ON
   emp.mgr = m.empno