How to use a return Varchar value from a function in where clause

Hi there

I have a function which returns a string i want to use this in where clause to return the serviceCode A, C or both. I trying to do it as follows. But doesn't return any data when i use it in select statement. Any idean why? or i would appreciate if you could please tell me the better way of doing it?

ALTER FUNCTION [dbo].[ret_ServiceCode]
	-- Add the parameters for the function here
	@ServiceCode int
RETURNS nvarchar(200)
	-- Declare the return variable here
	Declare @SerCode nvarchar(200)

	-- Add the T-SQL statements to compute the return value here
	If @ServiceCode = 1
		set @SerCode = 'Select ServiceCode from tblServiceCodes Where ServiceCode = A'
   Else  If @ServiceCode = 2
		set @SerCode ='Select ServiceCode from tblServiceCodes Where ServiceCode = C'
   Else  If @ServiceCode = 3
		set @SerCode ='Select ServiceCode from tblServiceCodes Where ServiceCode in(A,C)'

	-- Return the result of the function
	RETURN @SerCode


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and in my select statement i am using the function as
select * from tblPatient where ServiceCode in (dbo.ret_ServiceCode(1))

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can you please help
Ali ShahSQL DeveloperAsked:
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Vitor MontalvãoMSSQL Senior EngineerCommented:
It only returns a value, right?
Then use '=' instead of IN:
select * from tblPatient where ServiceCode = dbo.ret_ServiceCode(1)

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Scott PletcherSenior DBACommented:
You can't return query code and have it run dynamically.

You could use an inline-table-valued function to get the values:

ALTER FUNCTION [dbo].[ret_ServiceCode]
      @ServiceCode int
   Select ServiceCode
   From tblServiceCodes
   Where (@ServiceCode = 1 And ServiceCode = 'A')
      Or (@ServiceCode = 2 And ServiceCode = 'C')
      Or (@ServiceCode = 3 And ServiceCode IN ('A', 'C'))
GO --end function

select *
from tblPatient
where ServiceCode in (select servicecode from dbo.ret_ServiceCode(1))

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Walter RitzelSenior Software EngineerCommented:
The error is that you are returning a string containing a query, instead of the possible results.

Take a look on this documentation:
Ali ShahSQL DeveloperAuthor Commented:
Ah Thanks a lot. That works perfectly.
Kindest Regards
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