configure sort but how or not work?

I need 'only' have this how sql views code
...
ORDERING BY (fields1<fields2) ASC

in the Sort criteria there is a box SQL sort code:
if I write those nothing happens;

the sql views isn't changed; nothing is add in the sql code; why?

also if write example only the word test I not see in the sql; how work this box and how can
have this (fields1<fields2) ASC ?