Fixing SQL generation for queries selecting COUNT(DISTINCT...) w/ ORDER_BY

[nickveys]

Issue #306, and PR #329 broke compatibility with a couple of queries we were using. Two regressions were introduced.

First, if the COUNT(DISTINCT) had an alias applied to it, the alias would be used in the PARTITION BY value expression, which was invalid SQL, according to the Transact-SQL docs it cannot use aliases.

Second, if the query (already having a COUNT(DISTINCT) and order clause) itself used a select call like this:

Model.select('COUNT(DISTINCT)...')
     .select('something as x, something_else as y')
     ....
     .order(:something)

the outer select would lose some of the aliased columns due to the regex used when stripping out the aliases into select_frags.

Added a test to verify this, the issues are intertwined so it's just one test.

Thanks for the great gem!

[metaskills]

Closing this PR since it can not be applied to master now due to the 4.2 work.

http://metaskills.net/2015/01/25/activerecord-sqlserver-v4.2.0---code-name-kantishna/

Perhaps you can help solve some of these remaining issues instead. https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/milestones/4-2-stable