mysql索引案例分析

表结构

order (oid,date,uid,status,money,time)

oid主键  date 普通索引  uid用户id 普通索引  status 普通索引  

select * from order where status != 2

select * from order where status=0 or status=1

select * from order where status in(0,1)

select * from order where status = 0 union all select * from order where status = 1

结论：方案1最慢  ， 2，3 ，4 都能够命中索引

union all 肯定能够命中索引      直接告诉mysql怎么做耗费cpu最少

简单in能够命中索引

对于or新版的mysql能够命中索引

对于!=负向查询不能命中索引