Cross joins

The derived table of a cross join is the Cartesian product of the tables involved. Each record in the table to the left of the CROSS operator is linked to each record in the table to the right of the CROSS operator.

Example

Form the Cartesian product of the CUSTOMERS and ORDERS tables:

SELECT *	or	SELECT *
FROM customers, orders		FROM customers CROSS JOIN orders

Table CUSTOMERS

cust_ num	company	...
100	Siemens AG
101	Login GmbH
102	JIKO GmbH
...	...
106	Foreign Ltd.
107	Externa & Co KG

Table ORDER

order_ num	cust_ num	...
200	102
210	106
211	106
...	...
300	101
305	105

Derived table

cust_ num	company	...	order_ num	cust_ num	...
100	Siemens AG		200	102
101	Login GmbH		200	102
102	JIKO GmbH		200	102
...	...		...	...
106	Foreign Ltd.		200	102
107	Externa & Co KG		200	102
100	Siemens AG		210	106
101	Login GmbH		210	106
102	JIKO GmbH		210	106
...	...		...	...
106	Foreign Ltd.		210	106
107	Externa & Co KG		210	106
...	...		...	...
100	Siemens AG		305	105
101	Login GmbH		305	105
102	JIKO GmbH		305	105
...	...		...	...
106	Foreign Ltd.		305	105
107	Externa & Co KG		305	105

Cartesian product of the CUSTOMERS and ORDERS tables