Article ID: 243211 - View products that this article applies to.
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BUG #: 56516 (SQLBUG_70)
A query containing an IN clause of correlated subqueries that are unioned together performs slower on SQL Server 7.0 than on SQL Server 6.5 when the correlation clauses are redundant.
Microsoft has confirmed this to be a problem in SQL Server 7.0. This problem has been corrected in U.S. Service Pack 2 for Microsoft SQL Server 7.0. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
254561For more information, contact your primary support provider.
(https://support.microsoft.com/kb/254561/ )INF: How to Obtain Service Pack 2 for Microsoft SQL Server 7.0 and Microsoft Data Engine (MSDE) 1.0
The following is an example of the type of query that performs poorly:
The above query can rewritten as follows: