IF kategori is an integer then the first one is the proper way to query it.
The second one is forcing MySQL to convert a string to an int before
comparing. (At least I THINK that's the problem.)
Cal
*
* Cal Evans
* Senior Internet Dreamer
* http://www.calevans.com
*
----- Original Message -----
From: "Erlend Stromsvik" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, August 06, 2001 10:53
Subject: slow and fast query problem
> Hi
>
> (I hope I'm not asking to many 'stupid' questions... :)
>
> This query runs very fast (time 0.01 seconds):
> SELECT * from DB_GNIST.varer WHERE kategori = 24010 ORDER BY
utgivelses_aar
> DESC LIMIT 10;
>
> This one is slow (time 0.73seconds):
> SELECT * from DB_GNIST.varer WHERE kategori = '24010' ORDER BY
> utgivelses_aar DESC LIMIT 10;
>
> Fast (0.49 seconds):
> SELECT count(*) from DB_GNIST.varer WHERE kategori = '24010' ODER BY
> utgivelses_aar DESC LIMIT 10;
> slow (10.47seconds):
> SELECT count(*) from DB_GNIST.varer WHERE kategori = 24010 ODER BY
> utgivelses_aar DESC LIMIT 10;
>
> Fast (0.83)
> SELECT * from DB_GNIST.varer a LEFT JOIN DB_GNIST.vare_bilder b ON a.isbn
=
> b.isbn WHERE kategori = '24010' ODER BY utgivelses_aar DESC LIMIT 10;
> Slow (10.30)
> SELECT * from DB_GNIST.varer a LEFT JOIN DB_GNIST.vare_bilder b ON a.isbn
=
> b.isbn WHERE kategori = 24010 ODER BY utgivelses_aar DESC LIMIT 10;
>
>
> I can't seem to find the any documentation about how "col = 'something'"
is
> handled by mysql and how "col = something" is handled. They are obviously
> handled in different ways. If you look at the two first queries, the fast
> one is 73 times faster than the slow one. That's a huge difference.
>
> On the last two queries the one with "kategori = 24010" will return a few
> more records than the first one. But if I replace "=" with "LIKE" both
> queries returns the same number of records, but the first one will still
be
> much faster.
>
> Anyway, if I have missed something in the manual, please just tell me and
> I'll go back reading it.
>
>
> Erlend Stromsvik
>
>
>
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