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From:Ying Lu Date:June 8 2005 4:28pm
Subject:Re: 'Single quotation mark' makes different results for 'explain
select'
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By the way, I am using 4.0.18-log on i686.linux2.6.10.


> Greetings,
>
> I did the following two explain select ... According to whether I put 
> the single quotation mark or not, I will get totally different results:
>
> 1. Without single quotation mark:
>
> explain SELECT * FROM test T1 force index (idx_test)
> WHERE  *T1.STUDID = 0999999 AND T1.Prog_link = 6666*;
>
>
> +-------+--------+------------------------+---------+---------+---------------------------------+-------+-------------+
> 
>
> | table | type   | possible_keys          | key     | key_len | 
> ref                             | rows  | Extra       |
>
> +-------+--------+------------------------+---------+---------+---------------------------------+-------+-------------+
> 
>
> | T1    | ALL    | idx_test               | NULL    |    NULL | 
> NULL                            | 91230 | Using where |
>
> +-------+--------+------------------------+---------+---------+---------------------------------+-------+-------------+
> 
>
>
> 2. With single quotation mark:
> explain SELECT * FROM test T1 force index (idx_test)
> WHERE  *T1.STUDID = '0999999' AND T1.Prog_link = '6666'*;
>
>
> +-------+--------+------------------------+----------+---------+---------------------------------+------+-------------+
> 
>
> | table | type   | possible_keys          | key      | key_len | 
> ref                             | rows | Extra       |
>
> +-------+--------+------------------------+----------+---------+---------------------------------+------+-------------+
> 
>
> | T1    | ref    | idx_test               | idx_test |       7 | 
> const                           |   27 | Using where |
>
> +-------+--------+------------------------+----------+---------+---------------------------------+------+-------------+
> 
>
>
>
> Note:  . create index idx_test on test(studid, prog_link);
>           . in test table, studid is varchar(7), prog_link is varchar(4).
>
>
> Thanks a lot!
> Emi
>
>
>
>

Thread
Re: 'Single quotation mark' makes different results for 'explainselect'Ying Lu8 Jun
  • Re: 'Single quotation mark' makes different results for 'explain select'Dan Nelson8 Jun