mysql不同时间粒度下的分组统计
我们在做项目或者数据分析时，经常遇到这样的需求：统计不同时间粒度下的数据分布情况，例如，每一天中每个小时网站的访问量，某路口每半个小时通过的车辆数量等。对于此类的问题，一个sql简单的查询就能实现，故特此记录下，方便以后使用。
在MySQL中，我的表为：track 数据结构如下所示：
按天统计
SELECT DATE(TimeStart) AS date, COUNT(*) AS num FROM track WHERE Flag = 0 AND Duration >= 300 GROUP BY date ORDER BY date;
按小时统计
SELECT DATE_FORMAT(TimeStart, '%Y-%m-%d %H:00:00') AS time, COUNT(*) AS num FROM track WHERE Flag = 0 AND Duration >= 300 GROUP BY time ORDER BY time;
按半小时统计
SELECT time, COUNT( * ) AS num FROM ( SELECT Duration, DATE_FORMAT( concat( date( TimeStart ), ' ', HOUR ( TimeStart ), ':', floor( MINUTE ( TimeStart ) / 30 ) * 30 ), '%Y-%m-%d %H:%i' ) AS time FROM tarck WHERE Flag = 0 AND Duration >= 300 ) a GROUP BY DATE_FORMAT( time, '%Y-%m-%d %H:%i' ) ORDER BY time;
按N分钟统计
SELECT time, COUNT( * ) AS num FROM ( SELECT Duration, DATE_FORMAT( concat( date( TimeStart ), ' ', HOUR ( TimeStart ), ':', floor( MINUTE ( TimeStart ) / 10 ) * 10 ), '%Y-%m-%d %H:%i' ) AS time FROM tarck WHERE Flag = 0 AND Duration >= 300 ) a GROUP BY DATE_FORMAT( time, '%Y-%m-%d %H:%i' ) ORDER BY time;
基本思路：将datetime类型的时间转化为相应时间片的时间，例如将‘2017-03-01 01:08:19’ 转化为‘2017-03-01 01:00:00’，然后group by即可。
按分钟统计
将按小时统计的SQL语句稍微修改下，就可以实现按分钟统计
SELECT DATE_FORMAT(TimeStart, '%Y-%m-%d %H:%i:00') AS time, COUNT(*) AS num FROM track WHERE Flag = 0 AND Duration >= 300 GROUP BY time ORDER BY time;
参考资料： https://blog.csdn.net/u010946448/article/details/83752984
