SQL - INTERSECT Clause

The SQL INTERSECT clause/operator is used to combine two SELECT statements, but returns rows only from the first SELECT statement that are identical to a row in the second SELECT statement. This means INTERSECT returns only common rows returned by the two SELECT statements.
Just as with the UNION operator, the same rules apply when using the INTERSECT operator.

Syntax:

The basic syntax of INTERSECT is as follows:

SELECT column1 [, column2 ] FROM table1 [, table2 ] [WHERE condition] INTERSECT SELECT column1 [, column2 ] FROM table1 [, table2 ] [WHERE condition]

Here given condition could be any given expression based on your requirement.

Example:

Consider following two tables, (a) CUSTOMERS table is as follows:

+----+----------+-----+-----------+----------+ | ID | NAME | AGE | ADDRESS | SALARY | +----+----------+-----+-----------+----------+ | 1 | Ramesh | 32 | Ahmedabad | 2000.00 | | 2 | Khilan | 25 | Delhi | 1500.00 | | 3 | kaushik | 23 | Kota | 2000.00 | | 4 | Chaitali | 25 | Mumbai | 6500.00 | | 5 | Hardik | 27 | Bhopal | 8500.00 | | 6 | Komal | 22 | MP | 4500.00 | | 7 | Muffy | 24 | Indore | 10000.00 | +----+----------+-----+-----------+----------+

(b) Another table is ORDERS as follows:

+-----+---------------------+-------------+--------+ |OID | DATE | CUSTOMER_ID | AMOUNT | +-----+---------------------+-------------+--------+ | 102 | 2009-10-08 00:00:00 | 3 | 3000 | | 100 | 2009-10-08 00:00:00 | 3 | 1500 | | 101 | 2009-11-20 00:00:00 | 2 | 1560 | | 103 | 2008-05-20 00:00:00 | 4 | 2060 | +-----+---------------------+-------------+--------+

Now let us join these two tables in our SELECT statement as follows:

SQL> SELECT ID, NAME, AMOUNT, DATE FROM CUSTOMERS LEFT JOIN ORDERS ON CUSTOMERS.ID = ORDERS.CUSTOMER_ID INTERSECT SELECT ID, NAME, AMOUNT, DATE FROM CUSTOMERS RIGHT JOIN ORDERS ON CUSTOMERS.ID = ORDERS.CUSTOMER_ID;

This would produce following result:

+------+---------+--------+---------------------+
| ID   | NAME    | AMOUNT | DATE                |
+------+---------+--------+---------------------+
|    3 | kaushik |   3000 | 2009-10-08 00:00:00 |
|    3 | kaushik |   1500 | 2009-10-08 00:00:00 |
|    2 | Ramesh  |   1560 | 2009-11-20 00:00:00 |
|    4 | kaushik |   2060 | 2008-05-20 00:00:00 |
+------+---------+--------+---------------------+