Article ID: 225093 - Last Review: March 14, 2006 - Revision: 2.1

FIX: Poor Performance with Inner Join with Multiple LIKE Clauses Using Variables

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This article was previously published under Q225093

BUG #: 55032 (SQLBUG_70)

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SYMPTOMS

An inner join between two tables with multiple LIKE clauses produces a poor query plan if the LIKE clauses use variables instead of string literals.

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WORKAROUND

To work around this use one of the following:

Replace the variables with string constants.
Provide a hint to force a loop join. For example, use an INNER LOOP JOIN instead of an INNER JOIN.
Use the system stored procedure sp_executesql to execute the query, passing the variables as parameters. For syntax details see the Books Online article "sp_executesql (T-SQL)".

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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:

254561 (http://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

For more information, contact your primary support provider.

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MORE INFORMATION

The following conditions must be met to encounter this bug:

The query must contain an inner join.
The WHERE clause of the query must contain multiple LIKE predicates.
The LIKE predicates must be passed a variable, not a string constant (that is, "... AND column LIKE @myvar1 ...").

The inner join may use either ANSI-standard or Transact-SQL (TSQL) join syntax.

For example, the following query demonstrates this problem:

SELECT p.first_name
FROM person p
INNER JOIN customer c ON p.person_id = c.person_id 
WHERE p.last_name LIKE @last_name AND
   p.first_name LIKE @first_name

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