Question

Is it possible to declare that a column in MySQL should be unmodifiable once initially set? I have a column that has the following definition: created timestamp default current_timestamp and I’d like to make sure that nobody messes with it after my rows are created.

Answer 1

You can accomplish this using a BEFORE UPDATE trigger:

DELIMITER $$
    CREATE TRIGGER trFoo BEFORE UPDATE ON foo
    FOR EACH ROW BEGIN
      IF NEW.Bar != OLD.Bar THEN
        SET NEW.Bar = OLD.Bar;      
      END IF;
    END$$
DELIMITER ;