I think best way to learn about Inner and Outer Join is by looking at the result set. Do Following.

1- Connect as SCOTT/TIGER

2- Equi Join
Select e.ename, e.sal, e.empno, d.dname, d.deptno
from emp e, dept d
where e.deptno = d.deptno

3- Inner Join
Select e.ename, e.sal, e.empno, d.dname, d.deptno
from emp e, dept d
where e.deptno(+) = d.deptno
(This will also give you the deptno that does not have any employee such as Deptno 40)


4- Update emp
set deptno = NULL
where job = 'PRESIDENT'
(This will take out the president from the deptno 10)


5- Outer Join
Select e.ename, e.sal, e.empno, d.dname, d.deptno
from emp e, dept d
where e.deptno = d.deptno(+)
(This will give you the employee who is not associated with any deptno such as President)

Also look at the following website
http://databases.about.com/library/weekly/aa022501b.htm

[Edited by irehman on 08-30-2001 at 11:02 AM]