MySQL-在时间范围内分组日期和ID的行

Question

我在查询时遇到麻烦，我需要从数据库中获取一些数据。

我有一个包含以下数据的表：

id    user_id     game_id    date
1     1           1          2015-08-19
2     1           2          2015-08-19
3     1           3          2015-08-19
4     2           1          2015-08-20
5     2           2          2015-08-20
6     1           1          2015-08-20
7     1           1          2015-08-20
8     3           1          2015-08-20
9     2           1          2015-08-21
10    1           1          2015-08-21
11    1           2          2015-08-21
12    2           1          2015-08-21

我需要获取按日期和user_id分组的日期范围（即2015-08-10至2015-08-22）“玩过”的用户总数。 例如，使用给定的数据，结果应为：

total_players    date
1                2015-08-19
3                2015-08-20
2                2015-08-21

我已经在以下查询中尝试过此方法，但它无法正确分组：

SELECT date, COUNT(*) AS total_players 
FROM plays 
WHERE date BETWEEN '$start_date' AND '$end_date' 
GROUP BY date, user_id

有人可以帮助我提供正确的查询吗？ 提前谢谢大家。

Answer 1

SELECT date, COUNT(DISTINCT user_id) 
FROM plays
WHERE date BETWEEN '$start_date' AND '$end_date' 
GROUP BY date

使用您的数据在测试数据库上进行本地测试

total_players    date
1                2015-08-19
3                2015-08-20
2                2015-08-21

Answer 2

http://sqlfiddle.com/#!9/08957/3

SELECT `date`, COUNT(DISTINCT user_id) AS total_players 
FROM plays 
GROUP BY `date`

要么

SELECT `date`, COUNT(DISTINCT user_id) AS total_players 
FROM plays 
WHERE date BETWEEN '$start_date' AND '$end_date' 
GROUP BY `date`