MySQL 60天，90天和每日流失

Question

我一直致力于客户流失分析。我根据以下代码成功估算了每月流失率。这是我用过的代码

with monthly_usage as (
  select 
    who_identifier, 
    datediff(month, '1970-01-01', when_timestamp) as time_period
  from events
  where event = 'login' group by 1,2 order by 1,2),

lag_lead as (
  select who_identifier, time_period,
    lag(time_period,1) over (partition by who_identifier order by who_identifier, time_period),
    lead(time_period,1) over (partition by who_identifier order by who_identifier, time_period)
  from monthly_usage),

lag_lead_with_diffs as (
  select who_identifier, time_period, lag, lead, 
    time_period-lag lag_size, 
    lead-time_period lead_size 
  from lag_lead),

calculated as (select time_period,
  case when lag is null then 'NEW'
     when lag_size = 1 then 'ACTIVE'
     when lag_size > 1 then 'RETURN'
  end as this_month_value,

  case when (lead_size > 1 OR lead_size IS NULL) then 'CHURN'
     else NULL
  end as next_month_churn,

  count(distinct who_identifier)
   from lag_lead_with_diffs
  group by 1,2,3)

select time_period, this_month_value, sum(count) 
  from calculated group by 1,2
union
select time_period+1, 'CHURN', count 
  from calculated where next_month_churn is not null
order by 1

但是，我有兴趣计算60天，90天和每日流失。有什么方法可以调整这段代码吗？我是SQL新手，目前正在研究MySQL。我共享的代码已经转换为MySQL，输出如下。