Question

I have a situation where I need to keep track of all changes to the data in a MySQL database.

For example, we have a field in the “customers” table which will contain a rating that indicates how risky it is to do business with that customer. Whenever this field is changed, I need to have it logged so we can go back and say “well they were a 3 and now they are an 8,” for example. Is there any automated way to handle this in MySQL or am I just going have to write tons of change tracking logic into the application itself?

Answer 1

This is the type of thing that triggers are designed for inside of MySQL assuming you’re using a 5+ version of MySQL.

CREATE TRIGGER log_change_on_table BEFORE UPDATE ON customers
    FOR EACH ROW
        BEGIN
            INSERT INTO customer_log (customer_id, rating, date)
                VALUES (OLD.customer_id, OLD.rating, now())
        END $$