Question

在只有两列（id和dt）的表格中，我想计算过去3天内登录的唯一user_id的数量（dt是登录日期）对于任何给定的日期。这是我的数据样本：

id  dt
user_10 2015-09-01
user_9  2015-09-01
user_4  2015-09-01
user_8  2015-09-01
user_8  2015-09-02
user_9  2015-09-02
user_1  2015-09-02
user_6  2015-09-02
user_7  2015-09-03
user_3  2015-09-03
user_8  2015-09-03
user_10 2015-09-03
user_10 2015-09-04
user_9  2015-09-04
user_8  2015-09-04
user_4  2015-09-04
user_8  2015-09-04
user_6  2015-09-04

预期的输出是：

day count
2015-09-01  3
2015-09-02  5
2015-09-03  7
2015-09-04  8

以下是带有此数据的sqlfidle链接：http://sqlfiddle.com/#!9/ecda9
我尝试了几种方法，但我只能在数据的第一天得到正确的结果：

select t1.dt, count(distinct(t1.id)) from t as t1 INNER JOIN t t2
ON datediff(t1.dt,t2.dt)<=2
GROUP BY t1.dt
order by t1.dt

Answer 1

SELECT a.dt
     , COUNT(DISTINCT b.id) n 
  FROM t a 
  JOIN t b 
    ON b.dt BETWEEN a.dt - INTERVAL 3 DAY AND a.dt 
 GROUP 
    BY a.dt;

或调整您的解决方案......

select t1.dt
     , count(distinct(t2.id)) 
  from t as t1 
  JOIN t t2
    ON datediff(t1.dt,t2.dt) BETWEEN 0 AND 2
 GROUP 
    BY t1.dt
 order 
    by t1.dt;

MySQL - 根据滚动日期计算记录

1 个答案: