This article was previously published under Q235401
This article has been archived. It is offered "as is" and will no longer be updated.
BUG #: 55906 (SQLBUG_70)
Running an INSERT SELECT statement into a table that has a clustered index, in which all fields allow NULLs, may fail with the following error message:
Server: Msg 8623, Level 16, State 2, Line 5Internal Query Processor Error: The query processor could not produce a query plan.
This error only occurs if all of the following conditions are met:
The table has a clustered index in which all fields allow NULLs.
The clustered index fields are not referenced in the SELECT statement, so NULL values are to be inserted for all fields in the index.
A sufficient amount of rows are being inserted such that SQL Server determines it would be faster to sort the data before inserting into the clustered index.
Only one processor is available at the time the query plan is being generated. This could be for any of the following reasons:
The computer has a single processor.
The computer has multiple processors, but the Maximum Degree of Parallelism (MAX DOP) has been set to 1, either in sp_configure or with a query hint.
The computer has multiple processors, but is under such a sufficient load that they are all being utilized at the time the query plan is being generated.
When generating the plan for the sort with a single thread, the optimizer code does not expect NULL values for all of the fields to be sorted.
To work around this issue, choose any of the following options:
Change the clustered index to include at least one field that does not allow NULL values.
Change the clustered index to a non-clustered index.
Reference at least one of the clustered index keys in the INSERT SELECT statement so there are values inserted into the field.
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 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.