Math’s Set theory directly inspires SQL SET OPERATIONS. SQL SET OPERATIONS combine result sets from two or more SQL Queries into a single result set.
For SQL SET OPERATIONS
- The two queries must contain the same number of columns.
- Each column of the first query must be either the same data type as the corresponding column of the second query or convertible to the same data type as the corresponding column of the second query.
SQL has 4 SET OPERATORS.