PRB: Using a Self-Join to Produce a Cartesian Product

Last reviewed: April 25, 1997
Article ID: Q45493

The information in this article applies to:

  - Microsoft SQL Server version 4.2 for OS/2
  - Microsoft SQL Server version 4.2

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.

Additional query words: Transact-SQL Windows NT
Keywords : kbprg SSrvProg SSrvServer SSrvWinNT
Version : 4.2 | 4.2
Platform : OS/2 WINDOWS

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Last reviewed: April 25, 1997
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