select * from emp, dept
select * from emp, dept where emp.deptno = dept.deptno
select * from emp e, dept d
select e.ename, e.deptno, d.dname from emp e, dept d where e.deptno = d.deptno
select e1.ename, e1.job, e2.ename from emp e1 left join emp e2 on e1.mgr = e2.empno
/*****/
select e1.ename, e1.job, e2.ename, d.dname from (emp e1 left join emp e2 on e1.mgr = e2.empno) join dept d on e1.deptno = d.deptno
select e.ename,
e.job,
e.sal,
case
when e.sal >= 700 and e.sal <= 1200 then
'1'
when e.sal >= 1201 and e.sal <= 1400 then
'2'
when e.sal >= 1401 and e.sal <= 2000 then
'3'
when e.sal >= 2001 and e.sal <= 3000 then
'4'
else
'5'
end as grade
from emp e
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