4. Multi-table query

1. Check employee number 、 Name of employee 、 Wages 、 Name and location of Department

select empno,ename,sal,dname,loc
from emp e,dept d
where e.deptno=d.deptno

2. Check the employee's name 、 Wages 、 Entry time 、 Department number 、 Department name

select e.ename,e.sal,e.hiredate,d.deptno,d.dname 
from emp e,dept d
where e.deptno=d.deptno

3. Check the employee's name 、 Employee salary 、 Leader's name 、 Leader salary

select e.ename  Name of employee ,e.sal  Employee salary ,m.ename  Leader's name ,m.sal  Leader salary 
from emp e,emp m
where e.mgr=m.empno

4. Check the employee's name 、 Employee salary 、 Leader's name 、 Leader salary

select e.ename  Name of employee ,e.sal  Employee salary ,d.dname  Department name ,m.ename  Leader's name ,m.sal  Leader salary 
from emp e,dept d,emp m
where e.deptno=d.deptno and e.mgr=m.empno

5. Check the employee's name 、 Employee salary 、 Department name 、 Salary level

select e.ename  Name of employee ,e.sal  Employee salary ,d.dname  Department name ,s.grade  Pay scale 
from emp e,dept d,salgrade s
where e.deptno=d.deptno and e.sal between s.losal and s.hisal;

6. Check the employee's name 、 Employee salary 、 Department name 、 Employee pay scale 、 Leader's name 、 Leader salary 、 Salary grade of leaders

select e.ename  Name of employee ,e.sal  Employee salary ,d.dname  Department name ,s.grade  Employee pay scale ,m.ename  Leader's name ,m.sal  Leader salary ,sm.grade  Salary grade of leaders 
from emp e,dept d,salgrade s,salgrade sm
where e.deptno=d.deptno 
and e.sal between s.losal and s.hisal 
and e.mgr=m.empno 
and m.sal between sm.losal and sm.hisal;