You can't in that form. Create a procedure or view to do that for you.
(I assume it's for a fast selection menu with all characters of the alphabet ?) However you can check if there are entities with a name beginning with a given character using a scalar query and a LIKE predicate. (but that would take 26 (and probably even more) queries)
Yes that's it. The Quesry will return to me 5 elements and then
I wanetd to optimize and not going through all alphabet char but
I think I do not have achoice for that