Redshift的月号保留群组计算问题

Question

我试图在过去9个月内按月计算红移中的用户保留队列。但是我遇到了一个问题，即下面查询中的月份队列没有进入正确的月份。

我要查询的数据类型是：

userid - varchar activated-varchar

这是我正在尝试运行的查询：

with by_month as 
(SELECT
userid
DATE_TRUNC('month', cast ("activated" as date)) AS joined_month
FROM customers
GROUP BY 1, 2),

first_month as
(select userid, 
 joined_month,
 FIRST_VALUE(order_month) OVER (PARTITION BY userid ORDER BY 
 joined_month asc rows unbounded preceding) AS first
 FROM by_month),

 months as (select userid,
 joined_month,
 first,
 extract(month from (joined_month - first_month)) as month_number
 from first_month)


SELECT
 first as "cohort",
  SUM(CASE WHEN month_number = '0' THEN 1 ELSE 0 END) AS " Month 0",
  SUM(CASE WHEN month_number = '1' THEN 1 ELSE 0 END) AS " Month 1",
  SUM(CASE WHEN month_number = '2' THEN 1 ELSE 0 END) AS " Month 2",
  SUM(CASE WHEN month_number = '3' THEN 1 ELSE 0 END) AS " Month 3",
  SUM(CASE WHEN month_number = '4' THEN 1 ELSE 0 END) AS " Month 4",
  SUM(CASE WHEN month_number = '5' THEN 1 ELSE 0 END) AS " Month 5",
  SUM(CASE WHEN month_number = '6' THEN 1 ELSE 0 END) AS " Month 6",
  SUM(CASE WHEN month_number = '7' THEN 1 ELSE 0 END) AS " Month 7",
  SUM(CASE WHEN month_number = '8' THEN 1 ELSE 0 END) AS " Month 8",
   SUM(CASE WHEN month_number = '9' THEN 1 ELSE 0 END) AS " Month 9"
  from months
  where first_month >= '2018-08-01'
 GROUP BY 1 
ORDER BY 1 desc 

当我得到结果时，我得到了几个不可能的数字：

如：

Cohort       Month 0  Month 1
'2019-01-01'   95     120

我做了一些挖掘，发现月份数字没有被正确计算例如，对于'2019-01-01的队列，月份数量是正确捕获0,1和3，但是2正在错过归因于月份对修复有任何帮助，非常感谢谢谢！

Answer 1

现在，试试吧

SELECT userid, joined_month, first_month, month_number FROM months 
WHERE first = '2019-01-01' 

（随意添加其他列以深入研究问题）添加激活，order_month等，直到你得到正确处理它的原因。