Joins are of two types:
1. Inner Join – Matching column is given based on which joining the two tables occurs. all the rows which have a matching value of the column selected will be extracted. This is just like Intersection in sets. First find out all the matching values for the column selected for inner join, then return all the rows for this matching values.
2. Outer Join – Outer join is again divided into 3 types:
i Left Outer Join
ii Right Outer Join
iii Full Outer Join
In Left Outer join, unmatched column values for the first table are also extracted.
In right outer join, unmatched column values for the second table and matched column values for both the tables are extracted.
In full join, all the columns irrespective of matches are extracted.