if statement - 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.