A lot of people believe that a clustered index guarantees a *sort* order on output. But that's not what it does; it guarantees a *storage* order on disk.

See, for example, [this blog post][1], [a follow-up][2], and [this longer discussion][3].


  [1]: https://sqlserverfast.com/blog/hugo/2006/12/the-beatles-versus-the-stones/
  [2]: https://sqlserverfast.com/blog/hugo/2007/01/the-beatles-versus-the-stones-the-explanation/
  [3]: https://groups.google.com/forum/?hl=en&fromgroups#!topic/microsoft.public.sqlserver.programming/_CzO_sfyeJ4