Execute bellow commands to clean the database.
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;
FOR f IN (select object_name from user_objects where object_type = 'FUNCTION') LOOP
EXECUTE IMMEDIATE ('DROP FUNCTION ' || f.object_name);
END LOOP;
FOR t IN (select object_name from user_objects where object_type = 'TYPE') LOOP
EXECUTE IMMEDIATE ('DROP TYPE ' || t.object_name||' FORCE');
END LOOP;
FOR p IN (select object_name from user_objects where object_type = 'PROCEDURE') LOOP
EXECUTE IMMEDIATE ('DROP PROCEDURE ' || p.object_name);
END LOOP;
END;
