Beginner SQL section: avoiding repeated expression

Question

I\'m entirely new at SQL, but let\'s say that on the StackExchange Data Explorer, I just want to list the top 15 users by reputation, and I wrote something like this:

Answer 1

You CAN refer to RepInK in the Order By clause, but in the Where clause you must repeat the expression. But, as others have said, it will only be executed once.