SELECT u.uco_desc as DESCRIPTION,
u.uco_code as SIGNATURETYPE,
u.uco_rcode as SIGNATURECODE
FROM (
SELECT uco_code,uco_desc,uco_rcode
                FROM R5UCODES u 
                WHERE  <parameter.esigntype> IS NULL
                AND UCO_RCODE = '*' 
                AND uco_rentity = 'ESTP' 
UNION 
SELECT uco_code,uco_desc,uco_rcode
                FROM R5UCODES u 
                WHERE uco_rentity = 'ESTP' 
                AND UCO_RCODE = <parameter.esigntype>

     )  u
WHERE 1=1
