This works perfectly. But I was thinking, and I am asking just to understand the engine behind the process, this statement, ``` UPDATE t SET c3=c4, c4=c3; ``` uses temporary storage, correct? Because if the SQL goes from left to right, c3 will be over-written before it passes the old value to c4. So, something like this is happening in the background: ``` some-internal-temp = c3; c3 = c4; c4 = some-c-temp; ``` Just a newbie lack of knowledge question. Thanks. josé