Natalino,
Thursday, February 21, 2002, 1:46:11 PM, you wrote:
NP> Hi,
NP> I found that mysql doesn't used indexes if there is a <> in the where
NP> statement...
NP> for example
NP> mysql> explain select * from testtable where id <> 5;
NP> +---------+------+---------------+------+---------+------+-------+------------+
NP> | table | type | possible_keys | key | key_len | ref | rows | Extra |
NP> +---------+------+---------------+------+---------+------+-------+------------+
NP> | testtable | ALL | NULL | NULL | NULL | NULL | 13505 | where
NP> used |
NP> +---------+------+---------------+------+---------+------+-------+------------+
NP> 1 row in set (0.00 sec)
NP> please note that id is the primary key for the table...
It is not efficient in this case.
You can read in the manual how MySQL uses indexes:
http://www.mysql.com/doc/M/y/MySQL_indexes.html
NP> any ideas on how to optimize this type of queries ?
NP> Nat
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