Re: Select Distinct (was top N or rewriting MAX)

Jim Smith wrote:
>
> In article <32DEC3C1.7393_at_rci.rogers.com>, AWILSON
> <awilson_at_rci.rogers.com> writes
> >
> >How does Select Distinct work - ie what mechanism does it use to ensure
> >distinctness?
> It sorts the results and then does a table scan of the sorted set
> returning distinct rows. It may be able to use an index to achieve the
> same result, but in either case the ordering of the result is an
> accident.
>
> >Can it be relied upon to work the same way in future?
> >
> The safe answer is no, but I can't think of any mechanisms which would
> not result in a sorted set. Any clever computer science types out there
> who know of ways to achieve this?
> --
> Jim Smith

I think we can be quite sure of a sorted return BUT you may not be able to rely on whether it is sorted ascending or descending.

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