Basically Joins are used to get result from two or more tables and there are two types of joins inner join and outer join Inner join : a join of two or more tables which omits the blank rows while checking
Outer join is subcatogorised in to left outer join and right outer join. Which includes blank rows in specifed side if condition satisfies. Simple outer join is combination of left and right outerjoins. Apart from these there are Natural join : cartisian product Equi join : which includes operator in condition NonEqui join : All conditional joins which doesn't uses in there conditions.
Diffrent type of joins Natural join Inner join outer join cross join equi join non equi join self join to know the details go through the link given below http://www.tomjewett.com/dbdesign/dbdesign.php?page jointypes.php&imgsize medium
