This article was previously published under Q224539
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BUG #: 53568 (SQLBUG_70)
For queries that contain a predicate ... IN (a, b, c, ...), the SQL Server 7.0 optimizer evaluates the possibility of converting the query to a semi join. However, it fails to consider a similar simplification that would simplify a ... NOT IN (a, b, c, ...) as an anti semi join. Thus, a NOT IN query returning a similar number of rows may take considerably longer to run than a corresponding query using IN.
To work around this problem, explicitly create and populate an intermediate table with this list of values from the NOT IN clause, and rewrite the query using a join.
Microsoft has confirmed this to be a problem in SQL Server 7.0. This problem has been corrected in U.S. Service Pack 1 for Microsoft SQL Server 7.0. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
232570INF: How to Obtain Service Pack 1 for Microsoft SQL Server 7.0 and Microsoft Data Engine (MSDE) 1.0
For more information, contact your primary support provider.