How does the ORACLE statement delete foreign key constraints and create foreign key constraints

If there are main table test_main and sub table test_sub
SQL> -- Create foreign key (default option)
SQL> ALTER TABLE test_sub ADD CONSTRAINT main_id_cons FOREIGN KEY (main_id) REFERENCES test_main;
Table altered.

Delete foreign key constraint
ALTER TABLE test_sub DROP CONSTRAINT main_id_cons;

<!-- Baidu Button BEGIN -->