运行余额减少时如何删除和结转前一个月？

Question

我有以下数据：

client_id	balance_month	balance
100000000	September 1,2021 12:00 AM	00
100000000	August 1,2021 12:00 AM	00
100000000	July 1,2021 12:00 AM	00
100000000	June 1,2021 12:00 AM	00
100000000	May 1,2021 12:00 AM	000
100000000	April 1,2021 12:00 AM	00
100000000	March 1,2021 12:00 AM	[=11=]
200000000	September 1,2021 12:00 AM	00
200000000	August 1,2021 12:00 AM	00
200000000	July 1,2021 12:00 AM	00
200000000	June 1,2021 12:00 AM	00
200000000	May 1,2021 12:00 AM	00
200000000	April 1,2021 12:00 AM	00
200000000	March 1,2021 12:00 AM	[=11=]

我想用余额未减少的最近一个月覆盖余额减少的任何月份。（假设余额从 2021 年 3 月开始，但希望自动化的时间更长）

client_id	balance_month	balance
100000000	September 1,2021 12:00 AM	00
100000000	August 1,2021 12:00 AM	00
100000000	July 1,2021 12:00 AM	00
100000000	June 1,2021 12:00 AM	00
100000000	May 1,2021 12:00 AM	00
100000000	April 1,2021 12:00 AM	00
100000000	March 1,2021 12:00 AM	[=12=]
200000000	September 1,2021 12:00 AM	00
200000000	August 1,2021 12:00 AM	00
200000000	July 1,2021 12:00 AM	00
200000000	June 1,2021 12:00 AM	00
200000000	May 1,2021 12:00 AM	00
200000000	April 1,2021 12:00 AM	00
200000000	March 1,2021 12:00 AM	[=12=]

Answer 1

假设所有列 NOT NULL，否则您需要做更多。

SELECT client_id, balance_month
     , COALESCE(balance_null, first_value(balance_null) OVER (PARTITION BY client_id, balance_grp ORDER BY balance_month)) AS new_balance
FROM  (
   SELECT *
        , count(balance_null) OVER (PARTITION BY client_id ORDER BY balance_month) AS balance_grp
   FROM  (
      SELECT client_id, balance_month
           , CASE WHEN lead(balance) OVER (PARTITION BY client_id ORDER BY balance_month) < balance THEN NULL ELSE balance END AS balance_null
      FROM   tbl
      ORDER  BY client_id, balance_month
      ) sub1
   ) sub2;

db<>fiddle here

在子查询 sub1 中，如果下一行的 balance 较小（您的替换条件），则将 balance 设置为 NULL。

在子查询 sub2 中，为连续的 NULL 值形成组，包括使用 count(balance_null) 的前导非空值 (balance_grp)，因为它从计数中省略了 NULL 值，因此每个NULL 值属于具有最后一个有效（非空）值的组。

在外部 SELECT 中，将 NULL 值替换为每个组中的前导非空值。瞧。

如果可以假设 balance 在所有非违规行中稳定增长（或至少停滞），我们可以使用更简单的查询：

SELECT client_id, balance_month
     , COALESCE(balance_null, max(balance_null) OVER (PARTITION BY client_id ORDER BY balance_month))
FROM  (
   SELECT client_id, balance_month
        , CASE WHEN lead(balance) OVER (PARTITION BY client_id ORDER BY balance_month) < balance THEN NULL ELSE balance END AS balance_null
   FROM   tbl
   ORDER  BY client_id, balance_month
   ) sub1;

运行余额减少时如何删除和结转前一个月？

How to remove and carry forward month prior when running balance decreases?

sql

postgresql

window-functions

gaps-and-islands

运行 余额减少时如何删除和结转前一个月？

How to remove and carry forward month prior when running balance decreases?

sql

postgresql

window-functions

gaps-and-islands

运行余额减少时如何删除和结转前一个月？