求助，也不太清楚是属于引索还是查询

dimdark

那个工资等级指什么?其它如下图:

# 查询jack的工作地址
SELECT d.location FROM emp e INNER JOIN dept d ON e.deptno = d.deptno AND e.sname = 'jack';
# 查询工资比jack高的其他员工信息
SELECT e.sid, e.sname, e.sage, e.sjob, e.salary, d.deptno, d.dname, d.dtelephone, d.location FROM
  emp e INNER JOIN dept d ON e.deptno = d.deptno AND e.salary > 5100;
# 查询clink的工资等级(工资等级指什么)


# 查找和jack同部门的员工(输出时包括jack)
SELECT e.sname FROM emp e INNER JOIN dept d ON e.deptno = d.deptno AND e.deptno = 10;
# 若只知道jack,不知道jack的deptno值,则可以这样写:
SELECT e.sname FROM emp e INNER JOIN dept d ON e.deptno = d.deptno AND e.deptno IN (
  SELECT deptno FROM emp WHERE sname = 'jack');