This SQL tutorial explains how to use the SQL INTERSECT operator with syntax and examples.
The SQL INTERSECT operator is used to return the results of 2 or more SELECT statements. However, it only returns the rows selected by all queries. If a record exists in one query and not in the other, it will be omitted from the INTERSECT results.
Each SQL statement within the SQL INTERSECT must have the same number of fields in the result sets with similar data types.
The syntax for the SQL INTERSECT operator is:
SELECT expression1, expression2, ... expression_n FROM tables WHERE conditions INTERSECT SELECT expression1, expression2, ... expression_n FROM tables WHERE conditions;
The following is a SQL INTERSECT operator example that has one field with the same data type:
SELECT supplier_id FROM suppliers INTERSECT SELECT supplier_id FROM orders;
In this SQL INTERSECT example, if a supplier_id appeared in both the suppliers and orders table, it would appear in your result set.
The following is an INTERSECT example that uses a ORDER BY clause:
SELECT supplier_id, supplier_name FROM suppliers WHERE supplier_id > 2000 INTERSECT SELECT company_id, company_name FROM companies WHERE company_id > 1000 ORDER BY 2;
Since the column names are different between the two SELECT statements, it is more advantageous to reference the columns in the ORDER BY clause by their position in the result set. In this example, we've sorted the results by supplier_name / company_name in ascending order, as denoted by the "ORDER BY 2".
The supplier_name / company_name fields are in position #2 in the result set.