按 X 天范围分组

Question

我有一组或多条记录，我想对它们进行计数并按一定范围进行分组，例如我想对 X 天组创建的记录进行计数

e.g. SELECT COUNT(*) FROM `table` GROUP BY /*`created` 3 days/*

Answer 1

这是一个带有日期的示例。

create table t1(created date not null);

insert 
  into t1(created) values (date '2011-01-09')
                         ,(date '2011-01-10')
                         ,(date '2011-01-11')
                         ,(date '2011-01-12')
                         ,(date '2011-01-13')
                         ,(date '2011-01-14')
                         ,(date '2011-01-15')
                         ,(date '2011-01-16')
                         ,(date '2011-01-17')
                         ,(date '2011-01-18')
                         ,(date '2011-01-19')
                         ,(date '2011-01-20');

select floor(datediff(now(), created) / 3) * 3 as days_ago
      ,min(created)
      ,max(created)
      ,count(*)
  from t1
 group 
    by floor(datediff(now(), created) / 3);

+----------+--------------+--------------+----------+
| days_ago | min(created) | max(created) | count(*) |
+----------+--------------+--------------+----------+
|        0 | 2011-01-18   | 2011-01-20   |        3 |
|        3 | 2011-01-15   | 2011-01-17   |        3 |
|        6 | 2011-01-12   | 2011-01-14   |        3 |
|        9 | 2011-01-09   | 2011-01-11   |        3 |
+----------+--------------+--------------+----------+
4 rows in set (0.00 sec)

Answer 2

你可以做类似的事情
SELECT COUNT(*) FROM table GROUP BY FLOOR(created / 3)

...我想。

尽管如果 created 是日期字段，则您必须进行更多调整才能将其转换为数字值才能正常工作。

Answer 3

谢谢@Ronnis，我使用你的例子并最终解决了我的问题。

我发现了一个小错误，例如，我添加了一行

insert into t1(created) values (date '2011-01-21')

现在我得到：

+----------+--------------+--------------+----------+
| days_ago | min(created) | max(created) | count(*) |
+----------+--------------+--------------+----------+
|     1986 | 2011-01-20   | 2011-01-21   |        2 |
|     1989 | 2011-01-17   | 2011-01-19   |        3 |
|     1992 | 2011-01-14   | 2011-01-16   |        3 |
|     1995 | 2011-01-11   | 2011-01-13   |        3 |
|     1998 | 2011-01-09   | 2011-01-10   |        2 |
+----------+--------------+--------------+----------+

如您所见，天分为 2, 3, 3, 3, 2，这不是我所期望的。

我将 SQL 更改为

select floor(datediff(created, '2011-01-09') / 3) * 3 as days_before
      ,min(created)
      ,max(created)
      ,count(*)
from t1
group by floor(datediff(created, '2011-01-09') / 3);

Just get datediff 从创建到开始日期，现在我得到：

+-------------+--------------+--------------+----------+
| days_before | min(created) | max(created) | count(*) |
+-------------+--------------+--------------+----------+
|           0 | 2011-01-09   | 2011-01-11   |        3 |
|           3 | 2011-01-12   | 2011-01-14   |        3 |
|           6 | 2011-01-15   | 2011-01-17   |        3 |
|           9 | 2011-01-18   | 2011-01-20   |        3 |
|          12 | 2011-01-21   | 2011-01-21   |        1 |
+-------------+--------------+--------------+----------+

这可能更合适。