如何在mysql中的一个查询中选择和选择计数？

Question

我有这张桌子：

Activity     Date    
reading   12-10-2014
watching  12-10-2014
reading   13-10-2014
reading   12-10-2014
watching  13-10-2014 

我想要做的是选择活动并根据日期计算活动编号，我希望输出将是这样的（条件：日期=＆＃39; 12-10-2014＆＃39;）：

Activity   count    date
reading      2    12-10-2014
watching     1    12-10-2014

我该怎么办？请帮帮我。感谢。

Answer 1

SELECT Activity,COUNT(1) `count`,date
FROM mytable WHERE date='12-10-2014'
GROUP BY date,Activity;

或

SELECT Activity,COUNT(1) `count`,date
FROM mytable WHERE date='2014-10-12'
GROUP BY date,Activity;

确保您的表具有日期和活动

的索引

ALTER TABLE mytable ADD INDEX date_Activity_ndx (date,Activity);

Answer 2

这应该有效：

select activity, count(activity) as count, date from my_table
where date = '12-10-2014' group by activity;

（不确定您的列标签 - 您可能需要调整大小写）