mysql 索引

– 并没有添加索引,用时0.064s
select * FROM book WHERE title=’linkyang98526’
– 添加索引–用时0.474s
create index ia on book(title)
– 给title添加索引后是0.028s,
select * FROM book WHERE title=’linkyang93526’
– 删除索引 0.018s
drop index ia on book
– 唯一索引,与主键索引区别:允许字段值为null 0.431s
create UNIQUE INDEX ibon book (title)

– 添加索引后查询速度会变快,但是其他会变慢(插入,修改,)