SQL & PL/SQL

Hi
Please refer the query below. I want to avoid this error.
Please let me know, how do I manage this

SELECT uc1.*
FROM USER_CONSTRAINTS uc1
WHERE uc1.table_name = 'U1'
UNION
SELECT uc2.*
FROM USER_CONSTRAINTS uc1,
USER_CONSTRAINTS uc2
WHERE uc1.r_constraint_name = uc2.constraint_name
AND uc1.table_name = 'U1'
/

ORA-00997: illegal use of LONG datatype
00997. 00000 - "illegal use of LONG datatype"
*Cause:
*Action:
Error at Line: 95 Column: 12