我有这个表:MySQL不会使用索引进行查询吗?
CREATE TABLE `point` (
`id` INT(11) NOT NULL AUTO_INCREMENT,
`siteid` INT(11) NOT NULL,
`lft` INT(11) DEFAULT NULL,
`rgt` INT(11) DEFAULT NULL,
`level` SMALLINT(6) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `point_siteid_site_id` (`siteid`),
CONSTRAINT `point_siteid_site_id` FOREIGN KEY (`siteid`) REFERENCES `site` (`id`) ON DELETE CASCADE
) ENGINE=INNODB AUTO_INCREMENT=35 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci
而这个查询:
SELECT * FROM `point` WHERE siteid = 1;
导致此EXPLAIN信息:
+----+-------------+-------+------+----------------------+------+---------+------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+------+----------------------+------+---------+------+------+-------------+
| 1 | SIMPLE | point | ALL | point_siteid_site_id | NULL | NULL | NULL | 6 | Using where |
+----+-------------+-------+------+----------------------+------+---------+------+------+-------------+
的问题是,为什么不使用查询point_siteid_site_id索引?
我重新创建了你的表格,它清楚地使用了预期的索引。 – Nirmal 2010-04-03 15:29:21
当然不适合我,那是我为该查询收到的确切的EXPLIAN输出。 – 2010-04-06 21:12:13