使用 SQL 计算 7 天保留

Question

Given the following tables,

users                                             page_views
+-----------------+-----------+                  +----------+-----------+
| user_id                 |varchar| <----+       | pv_id     | varchar   |
| reg_ts                  |timestamp|            | pv_ts     | timestamp |
| reg_device              |varchar|       +----> | user_id   | varchar   |
| mktg_channel            |varchar|              | url       | varchar   |
+-----------------+-----------+                  | device    | varchar   |
                                                 +----------+-----------+

• Table "users" has one row per registered user.
• Table "page_views" has one row per page view event.

What % of users who first visit on a given day came back again 1 week later?

I'm currently using SQLlite and created a sample database but my output is off...

Below is what I have so far:

-- day 1 active users
SELECT *
FROM page_views
LEFT JOIN page_views AS future_page_views 
ON page_views.user_id = future_page_views.user_id
AND page_views.pv_ts = future_page_views.pv_ts - datetime(future_page_views.pv_ts, '+7 day')

-- day 7 retained users
SELECT 
  future_page_views.pv_ts,
  COUNT(DISTINCT page_views.user_id) as active_users,
  COUNT(DISTINCT future_page_views.user_id) as retained_users,
  CAST(COUNT(DISTINCT future_page_views.user_id) / COUNT(DISTINCT page_views.user_id) AS float) retention
FROM page_views
LEFT JOIN page_views as future_page_views 
ON page_views.user_id = future_page_views.user_id
AND page_views.pv_ts = future_page_views.pv_ts - datetime(page_views.pv_ts, '+7 day')
GROUP BY 1

Not sure if I should use Strftime function (DATEDIFF) in this instance to capture the 7 day. Open to any suggestions and feedback, thanks in advance.

EDIT** Sample data below, based on the below data set,

I expect only user_id (8) to show up as 7 day retained (first day 2020-01-02) (last day 2020-01-09)

Desired Output:

• User_ID
• p.pv_ts as First_Day
• f.pv_ts as Last_Day
• Retention Days (ie 1,2,3,4,5 days...)
• % of users who visited and came back on day 7

Answer 1

You can look at just the first two page visits and then aggregate. This gives

select user_id, min(pv_ts) as first_ts,
       nullif(max(pv_ts), min(pv_ts)) as second_ts
from (select pv.*,
             row_number() over (partition by user_id order by pv_ts) as seqnum
      from page_views pv
     ) pv
where seqnum <= 2
group by user_id;

Then to get the totals:

select count(*),
       sum(case when second_ts < datetime(first_ts, '+7day') then 1 else 0 end)
from (select user_id, min(pv_ts) as first_ts,
             nullif(max(pv_ts), min(pv_ts)) as second_ts
      from (select pv.*,
                   row_number() over (partition by user_id order by pv_ts) as seqnum
            from page_views pv
           ) pv
      where seqnum <= 2
      group by user_id
     ) u;