1.添加PRIMARY KEY（主键索引）
mysql>ALTER TABLE `table_name` ADD UNIQUE ( `column` )
mysql>ALTER TABLE `table_name` ADD INDEX index_name ( `column1`, `column2`, `column3` )
mysql>ALTER TABLE `table_name` ADD PRIMARY KEY ( `column` )
2.添加UNIQUE(唯一索引)
mysql>ALTER TABLE `table_name` ADD UNIQUE ( `column` )
3.添加INDEX(普通索引)
mysql>ALTER TABLE `table_name` ADD INDEX index_name ( `column` )
4.添加FULLTEXT(全文索引)
mysql>ALTER TABLE `table_name` ADD FULLTEXT ( `column`)
5.添加多列索引
mysql>ALTER TABLE `table_name` ADD INDEX index_name ( `column1`, `column2`, `column3` )
mysql 