MySQL - 计算不同月份记录的出现次数

Question

我有一个表格，其中包含我需要的所有信息，但格式不同。我想连接字段NAME和ACTIVITY以使其唯一，并按月和年分组我的日期。此查询将始终在2个日期之间进行比较，在我指定MONTH1时执行，实际表示分析的第一个月和分析的第二个月MONTH2。我还需要它们之间的差异百分比。

Example of Raw table:
======================
Name    Activity      Date
++++++++++++++++++++++++++++++++
Paul    VideoGame     2015-02-01
John    Play Guitar   2015-03-05
Paul    Play Guitar   2015-02-01
Paul    Play Guitar   2015-02-15
Paul    VideoGame     2015-03-04
John    Play Guitar   2015-03-06

Output wanted:
==================
Name+Activity      Month1     Month2   Percentage
+++++++++++++++++++++++++++++++++++++++++++++++++++
John+Play Guitar      0         2       +200%
Paul+VideoGame        1         1         0%
Paul+Play Guitar      2         0       -200%

Answer 1

如果你知道几个月，那么你可以通过条件聚合来做到这一点。我会将name和activity放在不同的列中。而且，我不太确定如何计算百分比列：

select name, activity,
       sum(month(date) = 2) as month1,
       sum(month(date) = 3) as month2,
       sum(month(date) = 3) - sum(month(date) = 2)) as diff
from rawtable
group by name, activity;

您可以将name和activity作为concat_ws('+', name, activity) if you really want. You can convert the diff`连接到您想要的格式乘以100。