fixes #590

[falti]

Run the test

$ rake test_mssql TEST=test/db/mssql/unit_test.rb

fixes #590

I could not run this fix against MS SQL database yet as I have some trouble with running this from a Mac.

[falti]

The Travis failures are completely unrelated to my change. I wonder if they upgraded Postgres in the meantime? There are actually 2 test runs which errored but they are in the "allowed to fail" group. I believe that this renders the status to failed. If somebody could please review and accept this PR as we really want this to be fixed soon.

[kares]

Hey Frank, thanks for the PR. not worries about CI. These will likely end up on the 1-3-stable branch.

I'm sorry but I'd like to keep this open as it is - since will likely want to get deeper with a review (at some point) ... MS-SQL support seems to be ping-pong bouncing back and forth. for now it seems that it's fine for most cases but I'm not sure if that code is not run when there's w e.g. an ORDER BY [nokings].id DESC while the main table is [vikings] than it would be actually worse than now (create an incorrect SQL).

[kares]

commits are picked on 1-3-stable and are expected to land in 1.3.18 ... thanks again for the PR