This article was previously published under Q281338
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BUG #: 26147 (SQLBUG_70)
Select distinct does not eliminate duplicate null values that are contained in bit datatype columns.
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.
Use the code that follows to reproduce this behavior:
create table #myTable( bar bit)goinsert into #mytable values (1)insert into #mytable values (1)insert into #mytable values (NULL)insert into #mytable values (NULL)goselect distinct bar from #mytablego
The preceding code returns this result:
bar ---- NULLNULL1
Note that the code correctly eliminates the duplicate value 1 but incorrectly returns duplicate null values. The correct resultset is: