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From:DBA Date:June 7 2005 9:22pm
Subject:Re: Seriously.. When are we going to get subqueries?!
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----- Original Message ----- 
From: "Kevin Burton" <burton@stripped>
To: <greg@stripped>
Cc: <mysql@stripped>
Sent: Tuesday, June 07, 2005 6:11 PM
Subject: Re: Seriously.. When are we going to get subqueries?!


> Greg Whalin wrote:
> 
>> They do use indexes if you use them to build derived tables and are 
>> pretty fast.  The only case where I see them not using indexes when I 
>> think they should is when you use a sub-query for an IN() clause.
> 
> I'm sorry.. yes.. They're not using indexes when within IN clauses which 
> for me is 99.9% of the time.
> 
> Maybe I'm wrong though and this is a rare but I don't think so...
> 
> Kevin

I use subqueries and I thought that it was using the index? I might be wrong? This is
MySQL on 4.1.11-nt. Here is the explain plan:

mysql> explain select count(*) from ptt_trans_06 where trans='ADD' and nai in (select
> scr_userid from ptt_home where number_of_sessions>3);
+----+--------------------+--------------+----------------+---------------+--------------+---------+------+-------+--------------------------+
| id | select_type        | table        | type           | possible_keys | key          |
key_len | ref  | rows  | Extra
           |
+----+--------------------+--------------+----------------+---------------+--------------+---------+------+-------+--------------------------+
|  1 | PRIMARY            | ptt_trans_06 | ALL            | NULL          | NULL         |
   NULL | NULL | 21621 | Using where
           |
|  2 | DEPENDENT SUBQUERY | ptt_home     | index_subquery | ptt_home_nai  | ptt_home_nai |
    250 | func |     1 | Using index; U
sing where |
+----+--------------------+--------------+----------------+---------------+--------------+---------+------+-------+--------------------------+

Isn't this using an index?

I would agree that I use a lot of subqueries using the IN()  clause.

Lawrence Kennon





Thread
Seriously.. When are we going to get subqueries?!Kevin Burton7 Jun
  • Re: Seriously.. When are we going to get subqueries?!Greg Whalin7 Jun
    • Re: Seriously.. When are we going to get subqueries?!Kevin Burton8 Jun
  • Re: Seriously.. When are we going to get subqueries?!DBA8 Jun
    • Re: Seriously.. When are we going to get subqueries?!Kevin Burton8 Jun
  • Re: Seriously.. When are we going to get subqueries?!Jeff Smelser8 Jun
    • Re: Seriously.. When are we going to get subqueries?!Dan Nelson8 Jun
      • Re: Seriously.. When are we going to get subqueries?!Jeff Smelser8 Jun
        • Re: Seriously.. When are we going to get subqueries?!Kevin Burton9 Jun
          • Re: Seriously.. When are we going to get subqueries?!Jochem van Dieten9 Jun
            • Re: Seriously.. When are we going to get subqueries?!Kevin Burton10 Jun
RE: Seriously.. When are we going to get subqueries?!Jay Blanchard8 Jun
  • Re: Seriously.. When are we going to get subqueries?!Jeff Smelser8 Jun
  • Re: Seriously.. When are we going to get subqueries?!Martijn Tonies8 Jun
  • RE: Seriously.. When are we going to get subqueries?!George Sexton9 Jun
    • Re: Seriously.. When are we going to get subqueries?!Jeff Smelser9 Jun
    • Re: Seriously.. When are we going to get subqueries?!Josh Trutwin9 Jun
    • Re: Seriously.. When are we going to get subqueries?!Keith Ivey9 Jun
      • Re: Seriously.. When are we going to get subqueries?!Jochem van Dieten9 Jun
      • Re: Seriously.. When are we going to get subqueries?!George L. Sexton9 Jun
RE: Seriously.. When are we going to get subqueries?!Jay Blanchard8 Jun
  • Re: Seriously.. When are we going to get subqueries?!Jeff Smelser8 Jun
  • Re: Seriously.. When are we going to get subqueries?!Greg Whalin8 Jun
    • Re: Seriously.. When are we going to get subqueries?!Kevin Burton9 Jun
RE: Seriously.. When are we going to get subqueries?!Jay Blanchard8 Jun
RE: Seriously.. When are we going to get subqueries?!PMilanese8 Jun
Re: Seriously.. When are we going to get subqueries?!Bob_Savard8 Jun
  • Re: Seriously.. When are we going to get subqueries?!Boyd Lynn Gerber9 Jun
RE: Seriously.. When are we going to get subqueries?!Jay Blanchard9 Jun
  • Re: Seriously.. When are we going to get subqueries?!Gordan Bobic9 Jun
  • RE: Seriously.. When are we going to get subqueries?!George Sexton9 Jun
RE: Seriously.. When are we going to get subqueries?!Jay Blanchard9 Jun
  • Re: Seriously.. When are we going to get subqueries?!Gordan Bobic9 Jun
    • Re: Seriously.. When are we going to get subqueries?!Josh Trutwin9 Jun
RE: Seriously.. When are we going to get subqueries?!Jay Blanchard9 Jun
RE: Seriously.. When are we going to get subqueries?!Jay Blanchard9 Jun
  • Re: Seriously.. When are we going to get subqueries?!Gordan Bobic9 Jun
RE: Seriously.. When are we going to get subqueries?!Jay Blanchard9 Jun
RE: Seriously.. When are we going to get subqueries?!Jay Blanchard9 Jun
  • RE: Seriously.. When are we going to get subqueries?!George Sexton9 Jun
RE: Seriously.. When are we going to get subqueries?!Jay Blanchard9 Jun
  • RE: Seriously.. When are we going to get subqueries?!George Sexton9 Jun
    • Re: Seriously.. When are we going to get subqueries?!Jeff Smelser9 Jun
      • Re: Seriously.. When are we going to get subqueries?!George L. Sexton9 Jun
        • Re: Seriously.. When are we going to get subqueries?!Roger B.A. Klorese 9 Jun
          • Re: Seriously.. When are we going to get subqueries?!Jochem van Dieten9 Jun
        • Re: Seriously.. When are we going to get subqueries?!Jeff Smelser9 Jun
          • Re: Seriously.. When are we going to get subqueries?!Greg Whalin9 Jun
            • Re: Seriously.. When are we going to get subqueries?!daniel9 Jun
              • Re: Seriously.. When are we going to get subqueries?!Jochem van Dieten9 Jun
  • Re: Seriously.. When are we going to get subqueries?!David Griffiths9 Jun
    • RE: Seriously.. When are we going to get subqueries?!J.R. Bullington9 Jun
Re: Seriously.. When are we going to get subqueries?!George L. Sexton9 Jun
RE: Seriously.. When are we going to get subqueries?!Bob)9 Jun
  • Re: Seriously.. When are we going to get subqueries?!Jochem van Dieten9 Jun
RE: Seriously.. When are we going to get subqueries?!Jay Blanchard9 Jun
RE: Seriously.. When are we going to get subqueries?!Gordon Bruce9 Jun
  • Timestamp and it's usage (Re: Seriously.. When are we going to get subqueries?!)Martijn Tonies9 Jun
    • Re: Timestamp and it's usage (Re: Seriously.. When are we going to get subqueries?!)Jochem van Dieten9 Jun
  • Re: Timestamp and it's usage (Re: Seriously.. When are we going to get subqueries?!)Martijn Tonies9 Jun