Using Parameters in DATEADD function of a Query - sql-server

Question

I am trying to us the DateAdd function of SQL in my Query. The problem is when I use a parameter to set the second arguement, the number argument I get an error which will say something like this:
Failed to convert parameter value from
a Decimal to a DateTime
While if I enter it parameterless, i.e hardcode an Int, it works fine.
This works:
SELECT FieldOne, DateField
FROM Table
WHERE (DateField> DATEADD(day, -10, GETDATE()))
while this does not:
SELECT FieldOne, DateField
FROM Table
WHERE (DateField> DATEADD(day, #days, GETDATE()))
Where #days = -10
Any ideas into what I am doing wrong? Incidentally I am setting this variable in SQL Server Manager, as I am trying to work out a bug in my DataAccess code. Not sure if that makes a difference.
Thanks

Answer 1

I know this is an old post, but for anyone else having this problem I had a similar issue in Reporting Services 2008 R2, although the error message was "Argument data type nvarchar is invalid for argument 2 of dateadd function." I think this issue could be related.
The problem was caused by the way Reporting Services parses the SQL code to generate a report dataset. In my case, I was able to change this dataset query:
SELECT DateAdd(wk, #NumWeeks, calendar_date) AS ToWeekFromDate
FROM dim_date
to this:
SELECT DateAdd(wk, Convert(Int, #NumWeeks), calendar_date) AS ToWeekFromDate
FROM dim_date
and the error was resolved.
EDIT: Just to expand on this answer a little: the issue was that Reporting Services was unable to parse the correct data type for #NumWeeks, I think possibly due to it being inside the DateAdd() function, and was defaulting it to NVarchar. Adding an explicit Convert() to set the data type to Int (even though it was already a number) enabled the parser to correctly identify the data type for #NumWeeks.

Answer 2

It sounds like you're passing the decimal as the 3rd instead of the 2nd parameter to DATEADD(), like:
DATEADD(day, GETDATE(), #days)
Although the snippet in the question looks fine.
(For extra clarity, the snippet above is an error. This is the code that would generate the error from the question.)

Answer 3

The following code works perfectly fine here (SQL Server 2005, executed in Management Studio):
DECLARE #days decimal
SET #days = -10
SELECT DATEADD(day, #days, GETDATE())
as does the following
DECLARE #days decimal
SET #days = -10
SELECT * FROM myTable WHERE myDate > DATEADD(day, #days, GETDATE())
So, the problem must lie somewhere else...

Answer 4

Are you sure the error is associated with this statement? There are no decimals involved and if I try this it still works
DECLARE #days decimal (19,6)
SET #days = -10.3346
--result is actually irrelevant
IF CAST(40000.6 AS decimal (19,6)) > DATEADD(day, #days, GETDATE())
SELECT 'yes'
ELSE
SELECT 'no'
Even trying to cast -10 decimal to smalldatetime this gives a different error
SELECT CAST(CAST(-10 AS decimal (19,6)) AS smalldatetime)
Msg 8115, Level 16, State 2, Line 1
Arithmetic overflow error converting expression to data type smalldatetime.