Creating Table User Defined Functions

FUNCTION "get_po_counts"( im_fdate DATE )
 RETURNS TABLE (EMAIL NVARCHAR(255),
	       FULLNAME NVARCHAR(255),
	       CREATE_CNT INTEGER,
	       CHANGE_CNT INTEGER,
	       COMBINED_CNT INTEGER)
    LANGUAGE SQLSCRIPT
    SQL SECURITY INVOKER AS
BEGIN

po_create_cnt =  SELECT COUNT(*) AS CREATE_CNT, "CREATEDBY" as EID
     FROM "OPENSAP_PURCHASEORDER_HEADERS" WHERE ID IN (
                     SELECT "POHEADER_ID"
                          FROM "OPENSAP_PURCHASEORDER_ITEMS"
          WHERE "PRODUCT_PRODUCTID" IS NOT NULL)
                 AND MONTH("CREATEDAT") = MONTH(:im_fdate)
            GROUP BY  "CREATEDBY";

po_change_cnt = SELECT COUNT(*) AS CHANGE_CNT, "MODIFIEDBY" as EID
     FROM "OPENSAP_PURCHASEORDER_HEADERS"  WHERE ID IN (
                     SELECT "POHEADER_ID"
                          FROM "OPENSAP_PURCHASEORDER_ITEMS"
          WHERE "PRODUCT_PRODUCTID" IS NOT NULL)
                AND MONTH("MODIFIEDAT") = MONTH(:im_fdate)
             GROUP BY  "MODIFIEDBY";

EMP_PO_COMBINED_CNT =
        SELECT EMAIL, "get_full_name"( "NAMEFIRST", "NAMEMIDDLE", "NAMELAST") as FULLNAME,
         crcnt.CREATE_CNT, chcnt.CHANGE_CNT,  crcnt.CREATE_CNT +
         chcnt.CHANGE_CNT AS COMBINED_CNT
            FROM "OPENSAP_MD_EMPLOYEES" as emp
            LEFT OUTER JOIN :PO_CREATE_CNT AS crcnt
             ON emp.email = crcnt.EID
           LEFT OUTER JOIN :PO_CHANGE_CNT AS chcnt
           ON emp.email = chcnt.EID
          ORDER BY COMBINED_CNT DESC;

return select * from :emp_po_combined_cnt;

END;