Posted by Captain Paralytic on 07/27/07 10:44

On 27 Jul, 11:31, gosha bine <stereof...@gmail.com> wrote:
> On 27.07.2007 11:46 Toby A Inkster wrote:
>
> > gosha bine wrote:
>
> >> Don't know about "most" ones, mysql docs explicitly says they're equivalent
> >>http://dev.mysql.com/doc/refman/5.0/en/distinct-optimization.html
>
> > It says that SELECT DISTINCT and GROUP BY *usually* end up generating the
> > same execution plan, so there won't be a performance difference.
>
> Pretending that you cannot read is probably the worst defense you could
> come up with. ;)
>
> --
> gosha bine
>
> makrell ~http://www.tagarga.com/blok/makrell
> php done right ;)http://code.google.com/p/pihipi

But it is you who cannot read!

The manual does NOT (neither explicitly not implicitly) say that GROUP
BY and DISTINCT are equivalent.

What it does say is:

"In most cases, a DISTINCT clause can be considered as a special case
of GROUP BY."

And it then says:

"For example, the following two queries are equivalent: ..."

The phrase "In most cases" implies that they are not equivalent. If
they were it would say "In all cases".

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