MySQL: update a field only if condition is met

Question

Is it possible to do an UPDATE query in MySQL which updates field value only if certain condition is met? Something like this:

UPDATE test SET     CASE         WHEN true         THEN field = 1     END WHERE id = 123 

In other words:

UPDATE test SET     something = 1,        /*field that always gets updated*/     CASE         WHEN true         THEN field = 1    /*field that should only get updated when condition is met*/     END WHERE id = 123 

What is the proper way to do this?

Answer 1

Yes!

Here you have another example:

UPDATE prices SET final_price= CASE    WHEN currency=1 THEN 0.81*final_price    ELSE final_price END 

This works because MySQL doesn't update the row, if there is no change, as mentioned in docs:

If you set a column to the value it currently has, MySQL notices this and does not update it.