In Oracle, constraints can be set up to enforce business rules on a database.
Sometimes you might want to remove constraints. To do this, use the ALTER TABLE command.
ALTER TABLE employee
DROP CONSTRAINT chk_emp_name;
You'll need to know the name of the constraint to do this. You can query the user_cons_columns view to find this:
SELECT *
FROM user_cons_columns
WHERE table_name = 'your_table_name';