I have a PDO mysql that updates 3 fields.

$update = $mypdo->prepare("UPDATE tablename SET field1=:field1, 
                                                field2=:field2, 
                                                field3=:field3 
                                            WHERE key=:key");

But I want field3 to be updated only when $update3 = true;

Is this possible to accomplish with a single query?

I could do it with 2 queries where I update field1 and field2 then check the boolean and update field3 if needed in a separate query. But hopefully there is a way to accomplish this in 1 query?