What do you mean by Outer Join? and define also how many types of Outer Join?
Outer Join is the bassically use for a rows. That join includes rows even if related rows in the joined table are absent is an Outer Join. We can create three different outer join to specify the unmatched rows to be included :
> Left Outer Join : In Left Outer Join all rows in the first& named table i.e. "left" table, which appears leftmost in the JOIN clause are included. Unmatched rows in the right table do not appear.
> Right Outer Join: In Right Outer Join all rows in the second;named table i.e. "right" table, which appears rightmost in the JOIN clause are included. Unmatched rows in the left table are not included.
> Full Outer Join: In Full Outer Join all rows in all joined tables are included, whether they are matched or not.