Hi.
On Thu 2002-07-25 at 10:41:54 +0200, [EMAIL PROTECTED] wrote:
[...]
> >>
> >>Personally I find the former much easier to read though not sure about
> >>the practical differences between them when the statements are executed.
> >
> >AFAICT, there should be no differences on execution speed.
> >
>
> We tested a lot with JOINS and found out, that the more expressions in
> the WHERE clause the slower it gets, this is very obvious of course, but
> it is surprisingly true for JOINS too.
If you mean writing "JOIN with ON clause" instead of ", with WHERE
clause", yes, that's because - AFAIK - both are converted to the same
internal representation. That's why I said, there should be no
difference.
> We tried to join about 10-15 tables together with LEFT JOIN and the old
> ','. The processing time differed drastically.
Of course, LEFT JOIN and "," (or INNER JOIN) are not the same thing.
LEFT JOIN has to do more work, depending on the table content. On the
other hand, LEFT JOIN fixes the join order, which can give a speed
benefit, if the optimizer chooses the wrong join order. You would have
to compare with STRAIGHT_JOIN set to exclude this.
> We tested this about 6 months ago with 3.23.36, so this may have be
> untrue now.
>
> BTW the processing time was about <1 second for the new syntax and
> up to 30 seconds for the old method.
Do you really mean "," with "old syntax" and "inner join" with "new
syntax"? I have a hard time believing this, as my experience is
differs.
Greetings,
Benjamin.
--
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