MySQL 聚合计数总和

Question

我有一个简单的分组查询:

SELECT timestamp, COUNT(users)
FROM my_table
GROUP BY users

如何添加 sum_each_day 列，该列将对每行的用户计数进行求和，并将其向前聚合到下一行，依此类推

输出应该是这样的:

timestamp | users | sum_each_day
2015-11-27  1          1
2015-11-28  5          6
2015-11-29  3          9
2015-11-30  7          16

提前致谢

Answer 1

您可以使用子查询，如下所示:

SELECT    timestamp,
          num_users,
          (SELECT COUNT(users)
           FROM   my_table
           WHERE  timestamp <= main.timestamp) sum_users
FROM      (
          SELECT   timestamp,
                   COUNT(users) num_users
          FROM     my_table
          GROUP BY timestamp
          ) main