FIX: "Attempting to set a non-NULL-able column's value to NULL" error message when you run a query that uses the ISNULL() function to select values of a nullable column in SQL Server 2008

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Article ID: 981037 - View products that this article applies to.
Microsoft distributes Microsoft SQL Server 2008 fixes as one downloadable file. Because the fixes are cumulative, each new release contains all the hotfixes and all the security fixes that were included with the previous SQL Server 2008 fix release.
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SYMPTOMS

Consider the following scenario:
  • In Microsoft SQL Server 2008, you run a query that uses the ISNULL() function to select values that are in a nullable column.
  • The table that contains the nullable column is joined with another table at the nullable column.
  • The query plan that is created by Query Optimizer uses a hash join, a spool, or a sort table below the JOIN operator.
In this scenario, you receive the following error message:
Msg 681, Level 16, State 3, Line 2
Attempting to set a non-NULL-able column's value to NULL.

CAUSE

Query Optimizer determines that the column that is referenced in the ISNULL() function is non-nullable because the join operator rejects NULL values. Then, in the query plan, Query Optimizer pushes the expression that is in the ISNULL() function below the JOIN operator. Additionally, the value of the expression can be NULL. However, Query Optimizer does not re-derive the nullability property for the expression. Then, in the query plan, a work table is used to implement the hash join, the spool, or the sort table that includes the expression. Additionally, the corresponding column in the work table is declared as non-nullable. When the SQL Server query engine tries to insert NULL values into the work table, the error occurs.

RESOLUTION

The fix for this issue was first released in Cumulative Update 7 for SQL Server 2008 Service Pack 1. For more information about this cumulative update package, click the following article number to view the article in the Microsoft Knowledge Base:
979065 Cumulative update package 7 for SQL Server 2008 Service Pack 1
Note Because the builds are cumulative, each new fix release contains all the hotfixes and all the security fixes that were included with the previous SQL Server 2008 fix release. We recommend that you consider applying the most recent fix release that contains this hotfix. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
970365 The SQL Server 2008 builds that were released after SQL Server 2008 Service Pack 1 was released
Microsoft SQL Server 2008 hotfixes are created for specific SQL Server service packs. You must apply a SQL Server 2008 Service Pack 1 hotfix to an installation of SQL Server 2008 Service Pack 1. By default, any hotfix that is provided in a SQL Server service pack is included in the next SQL Server service pack.

WORKAROUND

To work around this problem, use one of the following methods.

Method 1

Remove the ISNULL() function from the query.

Note Because the column that is in this function comes from the JOIN operator that rejects NULL values, the ISNULL() function is redundant.

Method 2

Rewrite the query so that the query plan does not use a hash join, a spool, or a sort table. For example, if your query contains an ORDER BY clause, create a clustered or covering index that provides required ordering and includes all required columns. When you use this method, Query Optimizer does not use a sort table.

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

REFERENCES

For information about the Incremental Servicing Model for SQL Server, click the following article number to view the article in the Microsoft Knowledge Base:
935897 An Incremental Servicing Model is available from the SQL Server team to deliver hotfixes for reported problems


For more information about the naming schema for SQL Server updates, click the following article number to view the article in the Microsoft Knowledge Base:
822499 New naming schema for Microsoft SQL Server software update packages


For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates

Properties

Article ID: 981037 - Last Review: March 15, 2010 - Revision: 1.1
APPLIES TO
  • Microsoft SQL Server 2008 Standard
  • Microsoft SQL Server 2008 Enterprise
  • Microsoft SQL Server 2008 Developer
  • Microsoft SQL Server 2008 Workgroup
Keywords: 
kbhotfixserver kbexpertiseadvanced kbsurveynew kbqfe kbfix KB981037

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