How to remove all the tables in a DB:
Please be careful in doing this!!!!!!!!!!!!!1


  BEGIN

FOR c IN (SELECT table_name FROM user_tables) LOOP
EXECUTE IMMEDIATE ('DROP TABLE ' || c.table_name || ' CASCADE CONSTRAINTS');
END LOOP;

FOR s IN (SELECT sequence_name FROM user_sequences) LOOP
EXECUTE IMMEDIATE ('DROP SEQUENCE ' || s.sequence_name);
END LOOP;

END;

Statement output:
anonymous block completed