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:

SELECT TOP 15
  DisplayName, Id, Reputation, Reputation/1000 As RepInK
FROM
  Users
WHERE
  RepInK > 10
ORDER BY Reputation DESC

Currently this gives an Error: Invalid column name 'RepInK', which makes sense, I think, because RepInK is not a column in Users. I can easily fix this by saying WHERE Reputation/1000 > 10, essentially repeating the formula.

So the questions are:

• Can I actually use the RepInK "column" in the WHERE clause?
  • Do I perhaps need to create a virtual table/view with this column, and then do a SELECT/WHERE query on it?
• Can I name an expression, e.g. Reputation/1000, so I only have to repeat the names in a few places instead of the formula?
  • What do you call this? A substitution macro? A function? A stored procedure?
• Is there an SQL quicksheet, glossary of terms, language specification, anything I can use to quickly pick up the syntax and semantics of the language?
  • I understand that there are different "flavors"?