How to create a function with dynamic sql or any better way to achieve this?

Question

        Hello,
        I have created below SQL query which works fine however when scalar function created ,it
        throws an error "Only functions and extended stored procedures can be executed from within a
        function.". In below code First cursor reads all client database names and second cursor
        reads client locations.
                  DECLARE @clientLocation nvarchar(100),@locationClientPath nvarchar(Max);
                  DECLARE @ItemID int;
                  SET @locationClientPath = char(0);
                  SET @ItemID = 67480;
   --building dynamic sql to replace database name at runtime
         DECLARE @strSQL nvarchar(Max);
         DECLARE @DatabaseName nvarchar(100);
         DECLARE @localClientPath nvarchar(MAX) ;
                  Declare databaselist_cursor Cursor for select [DBName] from [DataBase].[dbo].
                  [tblOrganization] 
                  OPEN databaselist_cursor
                  FETCH NEXT FROM databaselist_cursor INTO @DatabaseName
                  WHILE @@FETCH_STATUS = 0
                  BEGIN       
   PRINT 'Processing DATABASE: ' + @DatabaseName;
    SET @strSQL = 'DECLARE organizationlist_cursor CURSOR
    FOR SELECT '+ @DatabaseName +'.[dbo].[usGetLocationPathByRID]
                               ([LocationRID]) 
    FROM '+ @DatabaseName +'.[dbo].[tblItemLocationDetailOrg] where
                               ItemId = '+ cast(@ItemID as nvarchar(20))  ;
     EXEC sp_executesql @strSQL;
    -- Open the cursor
    OPEN organizationlist_cursor
    SET @localClientPath = '';
    -- go through each Location path and return the 
     FETCH NEXT FROM organizationlist_cursor into @clientLocation
     WHILE @@FETCH_STATUS = 0
      BEGIN
       SELECT @localClientPath =  @clientLocation; 
       SELECT @locationClientPath =
@locationClientPath + @clientLocation + ','
       FETCH NEXT FROM organizationlist_cursor INTO
@clientLocation
      END
       PRINT 'current databse client location'+  @localClientPath;
     -- Close the Cursor
     CLOSE organizationlist_cursor;
     DEALLOCATE organizationlist_cursor;
     FETCH NEXT FROM databaselist_cursor INTO @DatabaseName
                END
                CLOSE databaselist_cursor;
                DEALLOCATE databaselist_cursor;
                -- Trim the last comma from the string
               SELECT @locationClientPath = SUBSTRING(@locationClientPath,1,LEN(@locationClientPath)-  1);
                 PRINT @locationClientPath;
        I would like to create above query in function so that return value would be used in 
        another query select statement and I am using SQL 2005.
        I would like to know if there is a way to make this work as a function or any better way
        to  achieve this?
        Thanks,

Answer 1

This very simple: We 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 as per the microsoft..
In SQL 2005 and later, we could implement your function as a CLR function. Recall that all data access from the CLR is dynamic SQL. (here 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 and its not recommended too..
Raju Rasagounder Sr MSSQL DBA
      Hi Raju,
       Can you help me writing CLR for my above function? I am newbie to SQL CLR programming.
       Thanks in advance!
       Satya