MySQL calculate n-day retention rate

One 、 Create a table containing the earliest login date of each user

select user_id,min(date) as first_day
from a2_userbehavior_csv
group by user_id

Two 、 Create a table containing all login dates of each user

In fact, it means de duplication of users and dates

select user_id,date
from a2_userbehavior_csv
group by user_id,date

3、 ... and 、 Set the two tables according to user_id Splicing , And calculate the date time difference

select t1.*,t2.date,datediff(t2.date,t1.first_day) as day_diff
from 
(select user_id,min(date) as first_day
from a2_userbehavior_csv
group by user_id) as t1
left join 
(select user_id,date
from a2_userbehavior_csv
group by user_id,date) as t2
on t1.user_id=t2.user_id

The results are as follows ：

Get the number of days from each login date of each user to its earliest login date .

Four 、 Calculate various retention rates

Now the train of thought is clear .

Next day retention rate =（day_diff=1 The number of ）/（day_diff=0 The number of ）

Three day retention rate =（day_diff=3 The number of ）/（day_diff=0 The number of ）

... 

select first_day as dt,
	   concat(round(100*count(case when day_diff=1 then user_id end)/count(case when day_diff=0 then user_id end),2),"%") as ' Next day retention rate ',
	   concat(round(100*count(case when day_diff=3 then user_id end)/count(case when day_diff=0 then user_id end),2),"%") as ' Three day retention rate ',
	   concat(round(100*count(case when day_diff=7 then user_id end)/count(case when day_diff=0 then user_id end),2),"%") as ' Seven day retention rate '
from
(select t1.*,t2.date,datediff(t2.date,t1.first_day) as day_diff
from 
(select user_id,min(date) as first_day
from a2_userbehavior_csv
group by user_id) as t1
left join 
(select user_id,date
from a2_userbehavior_csv
group by user_id,date) as t2
on t1.user_id=t2.user_id) as t3
group by first_day 
order by first_day