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
>
>
>
>
