本月每周至少看电影的所有用户的列表

问题描述

create table active_users(
user_id numeric,
movie_streamed date
)


insert into active_users values (1,'2020-01-2'::date);

insert into active_users values (1,'2020-01-9'::date);

insert into active_users values (1,'2020-01-16'::date);

insert into active_users values (1,'2020-01-23'::date);

insert into active_users values (1,'2020-01-30'::date);

insert into active_users values (2,'2020-01-14'::date);

insert into active_users values (2,'2020-01-16'::date);

大家好，

我在寻找进行查询，这将帮助我获得本月每周至少看过一部电影的用户（即测试数据）。给定数据，其中每个记录都有user_id，并且特定人何时观看电影（给定日期）。我想要一个通用的答案。不像每个月都有4周。因为在某些情况下可能还会有5个星期的时间。

I am looking for a query which will help me to get the users who watched at least a movie every week in this month(being the test data). Given the data where every record has the user_id and when that particular person has watched the movie given the date. I want a generic answer. Not like every month has 4 weeks. Because there could be some scenarios where there are 5 weeks in some cases too.

推荐答案

您可以使用 generate_series（1,5）从1到5进行计数，因为应该有5个不同的星期存在，甚至如您已经提到的那样可能还没有完成。

You can use generate_series(1,5) by counting from 1 upto 5, since there should 5 different weeks might exist even uncompleted as you already mentioned.

技巧是比较当月内每周的开始日期的不同计数：

The trick is to compare the distinct count of the beginning dates for each week within the current month :

SELECT u.user_id  
  FROM active_users u 
  JOIN generate_series( 1, 5 ) g  
    ON date_trunc('week', movie_streamed) 
     = date_trunc('week', current_date) + interval '7' day * (g-1) 
 GROUP BY u.user_id
HAVING COUNT(DISTINCT date_trunc('week', movie_streamed))  = 
            (
             SELECT COUNT(*)
               FROM generate_series( 1, 5 ) g
              WHERE to_char(current_date,'yyyymm') 
                  = to_char(date_trunc('week', current_date) 
                    + interval '7' day * (g-1),'yyyymm')                  
            );

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