How to analyze the weekly activity rate?

【题目】

有两张表：

1）“用户登录信息表”,包含2个字段：用户id、登录日期.

2）“Registered user information form”,包含2个字段：用户id、注册日期.

【问题】Calculate the weekly active user rate.

【解题思路】

1. 活跃用户率

“活跃用户率”It is a common indicator to observe user activity,Generally refers to the proportion of active users among all registered users.When the active period is set to “周”时,计算的就是“Weekly active user rate”.

Weekly active user rate = 周活跃用户数 / The current number of registered users

值得注意的是,“The current number of registered users”Refers to the number of registered users as of the last day of the week.因为,Users registered after this will certainly not be active this week.

2. 日期处理

为了获取“用户登录信息表”中“登录日期”Information for the corresponding week,We need to do something with this field.

函数yearThe role is the year of the date,使用方法是：

year(日期字段名)

函数week的作用是返回一个int型的数值,Represents the week number information of the specified date in the current year,使用方法是：

week(日期字段名,参数)

其中,“参数”不填写的情况下,默认值为0,Sunday is the first day of the week;“参数”为1时,Means Monday is the first day of the week;“参数”为2时,Represents Tuesday as the first day of the week;以此类推.

select 用户id,
       登录日期,
       year(登录日期) as 年份,
       week(登录日期,1) as 周数
from 用户登录信息表;

返回结果如下：

The result is recorded as a tablet1,On this basis, the number of weekly active users is calculated.

select t1.年份,
       t1.周数,
       count(distinct 用户id) as 活跃用户数
from
(
select 用户id,
       登录日期,
       year(登录日期) as 年份,
       week(登录日期,1) as 周数
from 用户登录信息表
) as t1
group by t1.年份,t1.周数;

返回结果如下：

The result is recorded as a tablet2,The number of active users per week is recorded.

对“Registered user information form”的“注册日期”字段进行处理：

select 用户id,
       注册日期,
       year(注册日期) as 年份,
       week(注册日期,1) as 周数
from Registered user information form;

返回结果如下：

The result is recorded as a tablet3.

for later calculations“The current number of registered users”,需要获取“用户登录信息表”中的“Most active year”,以及对应的“Active maximum weeks”.

select year(max(登录日期)) as Most active year,
       week(max(登录日期),1) as Active maximum weeks
from 用户登录信息表;

返回结果如下：

The result is recorded as a tablet4.

3. 多表联结

In order to calculate each active week“The current number of registered users”,将表t3和表t4进行联结.

select count(distinct t3.用户id) as The current number of registered users
from
(
select 用户id,
       注册日期,
       year(注册日期) as 年份,
       week(注册日期,1) as 周数
from Registered user information form
) as t3
left join
(
select year(max(登录日期)) as Most active year,
       week(max(登录日期),1) as Active maximum weeks
from 用户登录信息表
) as t4 on 1 = 1
where t3.年份 < t4.Most active year or (t3.年份 = t4.Most active year and t3.周数 <= t4.Active maximum weeks);

返回结果如下：

The result is recorded as a tablet5.

最后,将表t2和表t5联结,计算最终结果：

select t2.年份,
       t2.周数,
       t2.活跃用户数,
       t5.The current number of registered users,
       t2.活跃用户数/t5.The current number of registered users as Weekly active user rate
from
(
select t1.年份,
       t1.周数,
       count(distinct 用户id) as 活跃用户数
from
(
select 用户id,
       登录日期,
       year(登录日期) as 年份,
       week(登录日期,1) as 周数
from 用户登录信息表
) as t1
group by t1.年份,t1.周数
) as t2
left join
(
select count(distinct t3.用户id) as The current number of registered users
from
(
select 用户id,
       注册日期,
       year(注册日期) as 年份,
       week(注册日期,1) as 周数
from Registered user information form
) as t3
left join
(
select year(max(登录日期)) as Most active year,
       week(max(登录日期),1) as Active maximum weeks
from 用户登录信息表
) as t4 on 1 = 1
where t3.年份 < t4.Most active year or (t3.年份 = t4.Most active year and t3.周数 <= t4.Active maximum weeks)
) as t5 on 1 = 1;

返回结果为：

【本题考点】

1）Check for user activity metrics“Weekly active user rate”的了解;

2）Test your ability to handle dates,比如week函数的使用;

3）考查对多表联结的了解.

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