1)
select emp.empno,emp.ename,emp.deptno,dept.loc,emp.sal,salgrade.grade
from emp,dept,salgrade
where emp.deptno=dept.deptno and emp.sal between salgrade.losal and salgrade.hisal;

2)
select emp.empno,emp.ename,emp.deptno,dept.loc,emp.sal,salgrade.grade
from emp,dept,salgrade
where emp.deptno=dept.deptno and emp.sal between salgrade.losal and salgrade.hisal
and salgrade.grade=4;

3)
select e.ename "Pracownik",e.job,e.hiredate,'   ' " ",m.ename "Manager",m.job,m.hiredate
from emp e,emp m
where e.mgr = m.empno and e.hiredate<m.hiredate;

4)
select a.ename "Wiecej zarabiajacy",a.sal,'   ',b.ename "Mniej zarabiajacy",b.sal
from emp a,emp b,salgrade c,salgrade d
where a.sal>b.sal and
a.sal between c.losal and c.hisal and c.grade=3 and
b.sal between d.losal and d.hisal and d.grade=3;

5)
select job from emp where deptno=10 MINUS select job from emp where deptno=20;