Truncate table with foreign keys

I have to truncate a table which gave me the below error.

ORA-02266: unique/primary keys in table referenced by enabled foreign keys.

I fixed that by checking the below,

SELECT p.table_name "Parent Table", c.table_name "Child Table", 
    p.constraint_name "Parent Constraint", c.constraint_name "Child Constraint" 
    FROM dba_constraints p 
    JOIN dba_constraints c ON(p.constraint_name=c.r_constraint_name) 
    WHERE (p.constraint_type = 'P' OR p.constraint_type = 'U') 
    AND c.constraint_type = 'R' AND p.table_name = UPPER('TABLE_NAME')
    AND p.owner='SCHEMA_NAME'
/

alter table schema.table_name disable constraint SYS_constraint_name;

truncated the table.

Now I am trying to enable the constraint but getting the below,

enable constraint ora-02298 cannot validate – parent keys not found

So I use the below query to identify the records in child table,

SELECT DISTINCT column_name FROM schema.table_name2 WHERE column_name NOT IN 
(
SELECT column_name FROM schema.table_name1
)

I am unable to delete the above as they have child tables which are acting as foreign keys.

Now my question – instead of going through loops deleting and disabling keys. How can I truncate a given table and not disable constraints