OUTER/INNER JOINS e.g

Question

Hi Gurus!
Can anyone explain with a really simple example(using say employee- department) tables, what is OUTER join, INNER join, Left RIGHT JOINs??
Thanks,
sapa

Answer 1

This question is only loosely related to the Oracle Migration Workbench,
however I included some information:
INNER JOINS are 'simple' joins where all matches, i.e. where both sides of the where clause are found, are returned.
LEFT OUTER JOIN, RIGHT OUTER JOIN and FULL OUTER JOIN [the OUTER keyword is optional] have the unmatched column and row filled in with nulls.
Oracle has its own (+) syntax but the new ANSI style as above in preferred, although the Oracle Migration Workbench does not generate ANSI style output yet.
An example use is where the owner may have no manager, but you might want the owner included in your selection of a hierarchy.
For more information see:
Oracle9i SQL Reference
Release 1 (9.0.1)
Part Number A90125-01
'SQL Queries and Other SQL Statements, 2 of 3'
http://otn.oracle.com/docs/products/oracle9i/doc_library/901_doc/server.901/a90125/queries2.htm#2054014
create table fulltable (col1 char(10), col2 char(10));
create table lefttable (col1 char(10), col2 char(10));
create table righttable (col1 char(10), col2 char(10));
insert into fulltable values ('one','1');
insert into fulltable values ('two','2');
insert into fulltable values ('three','3');
insert into lefttable values ('one','1');
insert into lefttable values ('two',null);
insert into lefttable values ('three','3');
insert into righttable values (null,'1');
insert into righttable values ('two','2');
insert into righttable values (null,'3');
SQL> select lefttable.col1, fulltable.col1 FROM lefttable, fulltable where left
table.col2(+)=fulltable.col2;
COL1 COL1
one one
two
three three
SQL> select lefttable.col1, fulltable.col1 FROM lefttable RIGHT JOIN fulltable
on lefttable.col2=fulltable.col2;
COL1 COL1
one one
three three
two
Turloch
Oracle Migration Workbench Team