某些mysql like查詢也是可以使用到索引的

當起始不是模糊查詢時，其實是可以用索引的

explain extended select * from users where email like '303578599%'

explain extended select * from users where email like '303%578599%'

如果起始就是模糊查詢，就要全表掃描了

explain extended select * from users where email like '%303578599%'