mysql 按天分组

Question

我有这个方案：

+-------+
|posts: |
+----+--+--------+--------------------+
| ID |   title   |      timestamp     |
+----+-----------+--------------------+
|  1 |    t1     |2011-04-05 17:54:55 |
+----+-----------+--------------------+ 
|  2 |    t2     |2011-04-06 09:10:11 |
+----+-----------+--------------------+ 
|  3 |    t3     |2011-04-07 02:07:22 |
+----+-----------+--------------------+ 

我如何获得过去 7 天的帖子总数，如下所示：

monday: 3
Tuesday: 9
Wednesday: 2

Answer 1

MySQL具体解决方案：

SELECT WEEKDAY(timestamp_field) AS wd, count(*) FROM your_table GROUP BY wd;

或

SELECT count(*) FROM your_table GROUP BY WEEKDAY(timestamp_field);

Answer 2

嗯，

您必须选择日期、计数 (*) 并按日期分组。

SELECT date_format(TIMESTAMP, '%d %m')
       , COUNT(*)
FROM posts
WHERE TIMESTAMP BETWEEN FROMDATE AND TODATE
GROUP BY date_format(TIMESTAMP, '%d %m')

进一步的帮助和解释： MySQL Manual for DATE_FORMAT

编辑：

平日也可以通过使用 %W 来实现。

Answer 3

SELECT WEEKDAY(timestamp), count(*)
FROM POSTS as p1
WHERE DATE_SUB(NOW(), INTERVAL 7 DAY) < timestamp
GROUP BY YEAR(timestamp), MONTH(timestamp), DAY(timestamp)
ORDER BY YEAR(timestamp) desc, MONTH(timestamp) desc, DAY(timestamp) desc

查看 MySQL 中的 date and time functions。