FIX: Select Distinct Fails to Eliminate Duplicate Null Values on Bit Datatype (281338)

The information in this article applies to:

Microsoft SQL Server 7.0

This article was previously published under Q281338

BUG #: 26147 (SQLBUG_70)

SYMPTOMS

Select distinct does not eliminate duplicate null values that are contained in bit datatype columns.

STATUS

Microsoft has confirmed this to be a problem in SQL Server 7.0. This problem has been corrected in U.S. Service Pack 3 for Microsoft SQL Server 7.0. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

274799 INF: How to Obtain Service Pack 3 for Microsoft SQL Server 7.0 and Microsoft Data Engine (MSDE) 1.0

For more information, contact your primary support provider.

MORE INFORMATION

Use the code that follows to reproduce this behavior:

create table #myTable( bar bit)
go
insert into #mytable values (1)
insert into #mytable values (1)
insert into #mytable values (NULL)
insert into #mytable values (NULL)
go
select distinct bar from #mytable
go

The preceding code returns this result:

bar  
---- 
NULL
NULL
1

Note that the code correctly eliminates the duplicate value 1 but incorrectly returns duplicate null values. The correct resultset is:

bar  
---- 
NULL
1

Modification Type:	Major	Last Reviewed:	3/14/2006
Keywords:	kbbug kbfix KB281338