he Join operation is one of the most useful activities in relational algebra. It is most commonly used way to combine information from two or more relations. A Join is always performed on the basis of the same or related column. Most complex queries of SQL involve JOIN command.
There are following types of join:
Inner joins: Inner join is of 3 categories. They are:
- Theta join
- Natural join
- Equi join
Outer joins: Outer join have three types. They are:
- Left outer join
- Right outer join
- Full outer join