MySQL - 统计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“名称”和“事件”以使其唯一，并按月和年对日期进行分组。此查询将始终在 2 个日期之间进行比较，当我指定 MONTH1(实际上意味着分析的第一个月)和 MONTH2(分析的第二个月)时执行以下操作。我还需要知道它们之间差异的百分比。

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

如果您知道月份，那么您可以通过条件聚合来完成此操作。我会将 name 和 activity 放在单独的列中。而且，我不太确定百分比列是如何计算的:

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;

如果您确实愿意，可以将 name 和 activity 连接为 concat_ws('+', name, Activity)。您可以通过乘以 100 将 diff` 转换为您想要的格式。