BUG: IN Subquery Reformats and Is Slower Than an Equivalent Join

ID: Q173314

The information in this article applies to:

• Microsoft SQL Server, versions 6.5 and 6.0

SYMPTOMS

A join combined with an IN subquery may cause a reformat access plan and be much slower than the logically equivalent pure join query. In general, an IN subquery should have approximately the same performance as the equivalent join.

WORKAROUND

Express the IN subquery as join, or break it down to several smaller queries using temporary tables, which collectively produce the same result.

STATUS

Microsoft has confirmed this to be a problem in Microsoft SQL Server versions 6.0 and 6.5. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

Additional query words: sub

Keywords          : kbusage SSrvGen kbbug6.50 kbbug6.00 
Version           : WINDOWS:6.0 6.5
Platform          : WINDOWS
Issue type        : kbbug

Last Reviewed: August 31, 1997