Inner Join is used to get the set of records that matches with in both the joined tables.
Union is used to get the Set of rows one of the other from multiple tables.
Union is used to get the Set of rows from a single table all as a single result set.
Union is having certain Rules like,
- The number and the order of columns should be same in all queries.
- The datatypes must be compatible.
- The Columns separated in the different select statements should be in same order.