是否可以做一个简单的查询来计算我在一个确定的时间段内有多少记录,比如一年,一个月,或者一天,有一个TIMESTAMP字段,比如:
SELECT COUNT(id)
FROM stats
WHERE record_date.YEAR = 2009
GROUP BY record_date.YEAR
甚至:
SELECT COUNT(id)
FROM stats
GROUP BY record_date.YEAR, record_date.MONTH
每月进行统计。
谢谢!
是否可以做一个简单的查询来计算我在一个确定的时间段内有多少记录,比如一年,一个月,或者一天,有一个TIMESTAMP字段,比如:
SELECT COUNT(id)
FROM stats
WHERE record_date.YEAR = 2009
GROUP BY record_date.YEAR
甚至:
SELECT COUNT(id)
FROM stats
GROUP BY record_date.YEAR, record_date.MONTH
每月进行统计。
谢谢!
当前回答
我更喜欢这样优化一年期组的选择:
SELECT COUNT(*)
FROM stats
WHERE record_date >= :year
AND record_date < :year + INTERVAL 1 YEAR;
这样你就可以把年份绑定在一起。'2009',带有命名参数,无需担心添加'-01-01'或单独传入'2010'。
另外,假设我们只是计算行数,id从不为NULL,我更喜欢COUNT(*)而不是COUNT(id)。
其他回答
或者你可以像这样使用group by子句,
//to get data by month and year do this ->
SELECT FORMAT(TIMESTAMP_COLUMN, 'MMMM yy') AS Month, COUNT(ID) FROM TABLE_NAME GROUP BY FORMAT(TIMESTAMP_COLUMN, 'MMMM yy')
如果要按日期获取记录,则在组中按格式更改为 'dd-mm-yy'或'dd-MMMM-yyy'
GROUP BY DATE_FORMAT(record_date, '%Y%m')
Note (primarily, to potential downvoters). Presently, this may not be as efficient as other suggestions. Still, I leave it as an alternative, and a one, too, that can serve in seeing how faster other solutions are. (For you can't really tell fast from slow until you see the difference.) Also, as time goes on, changes could be made to MySQL's engine with regard to optimisation so as to make this solution, at some (perhaps, not so distant) point in future, to become quite comparable in efficiency with most others.
如果你的搜索已经超过几年了,你仍然想每月分组,我建议:
版本1:
SELECT SQL_NO_CACHE YEAR(record_date), MONTH(record_date), COUNT(*)
FROM stats
GROUP BY DATE_FORMAT(record_date, '%Y%m')
版本#2(更有效):
SELECT SQL_NO_CACHE YEAR(record_date), MONTH(record_date), COUNT(*)
FROM stats
GROUP BY YEAR(record_date)*100 + MONTH(record_date)
我在一个大表上比较了这些版本,有1,357,918行(innodb), 第二个版本的效果似乎更好。
版本1(平均执行10次):1.404秒 版本2(平均执行10次):0.780秒
(增加SQL_NO_CACHE键,防止MySQL对查询进行缓存。)
试一试
按年(record_date),月(record_date)分组
如果你想获得一个每月统计数据,每个月的行数按最近一个月排序,那么试试这个:
SELECT count(id),
YEAR(record_date),
MONTH(record_date)
FROM `table`
GROUP BY YEAR(record_date),
MONTH(record_date)
ORDER BY YEAR(record_date) DESC,
MONTH(record_date) DESC