PRB: Using a Self-Join to Produce a Cartesian Product (45493)

The information in this article applies to:

Microsoft SQL Server 4.2x

This article was previously published under Q45493

SYMPTOMS

In attempting to produce the Cartesian product of a table with itself, a self-join without a WHERE clause produces only the table itself.

CAUSE

A self-join without a WHERE clause does not produce a Cartesian product unless the two instances of the table are given aliases and the select list includes columns from both aliases. The following does not produce a Cartesian product:

   select * from t1,t1

WORKAROUND

The following does produce a Cartesian product:

   select x.c1,y.c1 from t1 x, t2 y

This is the intended operation of SQL Server.

Modification Type:	Minor	Last Reviewed:	3/14/2005
Keywords:	kbProgramming KB45493