1.添加PRIMARY KEY(主键索引)
ALTER TABLE `table_name` ADD PRIMARY KEY ( `column` )
2.添加UNIQUE(唯一索引)
ALTER TABLE `table_name` ADD UNIQUE ( `column` )
3.添加INDEX(普通索引)
ALTER TABLE `table_name` ADD INDEX index_name ( `column` )
4.添加FULLTEXT(全文索引)
ALTER TABLE `table_name` ADD FULLTEXT ( `column`)
5.添加多列索引
ALTER TABLE `table_name` ADD INDEX index_name ( `column1`, `column2`, `column3` )
最常见的就是 3、5这两种方式了,如:
现有一张表:
DROP TABLE IF EXISTS `project`;
CREATE TABLE `project` (
`p_id` varchar(32) NOT NULL,
`p_name` varchar(64) DEFAULT NULL,
`p_intr` text,
`p_save` varchar(512) DEFAULT NULL,
`p_ctime` datetime DEFAULT NULL,
PRIMARY KEY (`p_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
对它加主键索引:
ALTER TABLE `project` ADD PRIMARY KEY ( `p_id` )
对它加组合索引:
ALTER TABLE `project` ADD INDEX select_by_id_name KEY ( `p_id`, `p_name` )
这里需要注意索引顺序( p_id
, p_name
)
如果你这么查询:
select * from project
where p_name
=? and p_id
=?
这是不会用到索引的,应该按下面这样:
select * from project
where p_id
=? and p_name
=?
顺序一定要按建索引的来,也可以在查询语句前加上EXPLAIN查看过程:
EXPLAIN select * from project
where p_id
=? and p_name
=?