Call dynamic SQL from function - sql

Question

I am writing a function that returns a table. There are two parameters that are passed to the function and a query is built and executed and inserted into the returning table. However I am receiving this error.
Only functions and some extended stored procedures can be executed from within a function.
I would like to not use a stored procedure as this is a simple utility function. Does anyone know if this can be done. My function is coded below, it checks for dupes for a certain column within a certain table.
-- =============================================
-- AUTHOR: JON AIREY
-- THIS FUNCTION WILL RETURN A COUNT OF HOW MANY
-- TIMES A CERTAIN COLUMN VALUE APPEARS IN A
-- TABLE. THIS IS HELPFUL FOR FINDING DUPES.
-- THIS FUNCTION WILL ACCEPT A COLUMN NAME, TABLE
-- NAME (MUST INCLUDE SCHEMA), AND OPTIONAL
-- DATABASE TO USE. RESULTS WILL BE RETURNED AS
-- A TABLE.
-- =============================================
ALTER FUNCTION [dbo].[fn_FindDupe]
(
-- Add the parameters for the function here
#Column VARCHAR(MAX),
#Table VARCHAR(100),
#Database VARCHAR(100) = ''
)
RETURNS
#TempTable TABLE
([Column] varchar(100)
,[Count] int)
AS
BEGIN
DECLARE #SQL VARCHAR(MAX)
SET #Table = CASE
WHEN #Database = ''
THEN #Table
ELSE #Database + '.' + #Table
END
SET #SQL =
'
INSERT INTO #TempTable
SELECT ' + #Column + '
,COUNT(' + #Column + ') AS CNT
FROM ' + #Table + '
GROUP BY ' + #Column + '
ORDER BY CNT DESC
'
EXEC SP_EXECUTESQL #SQL
RETURN
END
GO

Answer 1

You can't use dynamic sql in a udf:
This very simple: you cannot use dynamic SQL from used-defined
functions written in T-SQL. This is because you are not permitted do
anything in a UDF that could change the database state (as the UDF may
be invoked as part of a query). Since you can do anything from dynamic
SQL, including updates, it is obvious why dynamic SQL is not
permitted.
...
In SQL 2005 and later, you could implement your function as a CLR
function. Recall that all data access from the CLR is dynamic SQL.
(You are safe-guarded, so that if you perform an update operation from
your function, you will get caught.) A word of warning though: data
access from scalar UDFs can often give performance problems.