How to extarct DDL of table in oracle fusion HCM/FSCM

Hi,

We need to extarct DDL for few tables like column name, data type, size, primary key , foreign key constraints .
We tried sql query approach but due to data type size limitation not able to achieve it using sql query.
Like below query is giving appropriate result for PER_PEOPLE_GROUPS but failing for PER_ALL_ASSIGNMENTS_M.

WITH pk_columns AS (
SELECT acc.column_name
FROM all_cons_columns acc
JOIN all_constraints ac ON acc.constraint_name = ac.constraint_name
WHERE ac.constraint_type = 'P'
AND UPPER(ac.table_name) = UPPER(:p_table_name)
AND UPPER(ac.owner) = UPPER(:p_owner)