常用sql操作

1. 统计查询结果的数量

   select count(*) from  table

2. 查询时间时加8小时

   select * from table where date_add(time,interval 8 hour)> '2016-10-01 10:00:00'

3. 修改字段属性

   alter table `{$installer->getTable('memebox_auth/device')}`
          modify `device_id` varchar(256);

4. 联合查询join

   select * from A left join B on A.id=B.id where A.ctime>'2016-01-01' and B.status=0

5. 分组group by

   select status,count(*) from order group by status