'Simple' SQL Problem selecting null dates

Hi,
This really should be simple, but I'm having strange behaviour on the following code:
This works fine (returns 31 rows):
DECLARE @numInstances int
EXEC      @numInstances = sp_executesql N'SELECT     COUNT(*) AS numInstances
FROM         xjrvw_TR_Instances
WHERE     (fkResponsiblePersonId = @ResponsiblePersonId) AND (fkOrganizationId = @OrganizationId) AND (TraceDate IS
NULL)',N'@ResponsiblePersonId int,@OrganizationId int',@ResponsiblePersonId=1,@OrganizationId=2

This returns 0 rows:
DECLARE @numInstances int
EXEC      @numInstances = sp_executesql N'SELECT     COUNT(*) AS numInstances
FROM         xjrvw_TR_Instances
WHERE     (fkResponsiblePersonId = @ResponsiblePersonId) AND (fkOrganizationId = @OrganizationId) AND (TraceDate IS
NULL)',N'@ResponsiblePersonId int,@OrganizationId int',@ResponsiblePersonId=1,@OrganizationId=2
GO
And this also returns 0 rows (from the SQL Profiler when I run through the app)
DECLARE @numInstances int
EXEC      @numInstances = sp_executesql N'SELECT     COUNT(*) AS numInstances
FROM         xjrvw_TR_Instances
WHERE     (fkResponsiblePersonId = @ResponsiblePersonId) AND (fkOrganizationId = @OrganizationId) AND (TraceDate IS
NULL)',N'@ResponsiblePersonId int,@OrganizationId int',@ResponsiblePersonId=1,@OrganizationId=2
GO

I have tried changing it to a store procedure, to no avail.  The problem is definitely with the TraceDate IS NULL  - it works without that part of the predicate. I tried TraceDate.ISNULL = 1 but it tells me 'Cannot call methods on datetime.'

Can anyone please help?  I need to run it through the app, which interprets the top code to the second version.  

Thanks!
Carol.

exec sp_executesql N'SELECT     COUNT(*) AS numInstances
FROM         xjrvw_TR_Instances
WHERE     (fkResponsiblePersonId = @ResponsiblePersonId) AND (fkOrganizationId = @OrganizationId) AND (TraceDate IS 
NULL)',N'@ResponsiblePersonId int,@OrganizationId int',@ResponsiblePersonId=1,@OrganizationId=2
GO
DECLARE @numInstances int
EXEC	@numInstances = sp_executesql N'SELECT     COUNT(*) AS numInstances
FROM         xjrvw_TR_Instances
WHERE     (fkResponsiblePersonId = @ResponsiblePersonId) AND (fkOrganizationId = @OrganizationId) AND (TraceDate IS 
NULL)',N'@ResponsiblePersonId int,@OrganizationId int',@ResponsiblePersonId=1,@OrganizationId=2
GO
DECLARE @ResponsiblePersonId int
SET @ResponsiblePersonId = 2
DECLARE @OrganizationId int
SET @OrganizationId=1
SELECT     COUNT(*) AS numInstances
FROM         xjrvw_TR_Instances
WHERE     (fkResponsiblePersonId = @ResponsiblePersonId) AND (fkOrganizationId = @OrganizationId) AND (TraceDate IS 
NULL)

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jrepdevAsked:
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vinurajrCommented:
try with isnull(TraceDate,1)=1 or TraceDate is null
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jrepdevAuthor Commented:
Thanks.  Nice try, but that didn't work either...  It doesn't fail, just returns 0 rows instead of 31.  I could mention that this is being implemented via an .xsd using C#, not that it will help :-)

I appreciate your help,
Carol.
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Raja Jegan RSQL Server DBA & Architect, EE Solution GuideCommented:
I hope this issue is with respect to your ANSI_NULL settings in SQL Server 2005.

When SET ANSI_NULLS is ON, a SELECT statement that uses WHERE column_name = NULL returns zero rows even if there are null values in column_name. A SELECT statement that uses WHERE column_name <> NULL returns zero rows even if there are nonnull values in column_name.

When SET ANSI_NULLS is OFF, the Equals (=) and Not Equal To (<>) comparison operators do not follow the SQL-92 standard. A SELECT statement that uses WHERE column_name = NULL returns the rows that have null values in column_name. A SELECT statement that uses WHERE column_name <> NULL returns the rows that have nonnull values in the column. Also, a SELECT statement that uses WHERE column_name <> XYZ_value returns all rows that are not XYZ_value and that are not NULL.

Referred from http://msdn.microsoft.com/en-us/library/ms188048(SQL.90).aspx

If you have ANSI_NULLS ON, then use IS NULL in where condition
If you have ANSI_NULLS OFF, then use = NULL in where condition.
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jrepdevAuthor Commented:
Actually, my problem was much simpler - I'd transposed the values for the parameters!  However, that was a really interesting post - thank you - I didn't know that about Ansi Nulls.
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Microsoft SQL Server 2005

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