SQL 中的过期演变

Question

尽管我努力了，但我还是想不出一种方法来满足我的需求：

我有 2 个 table 分别包含一组要偿还的贷款和一组这些贷款的偿还（并非所有贷款都有偿还条目 table 因为其中一些仍未支付）。

Table 贷款有列：

id
数量
due_date

Table 报销有列：

id
debt_id
payment_date

我的目标是获取过去每个日期逾期5天以上的金额。

这是我所在的位置（在 Postgres 语法中）：

with due_for_5_days_by_date AS (
    select 
    due_date + interval '5' DAY as due_date,
    sum(amount) as amount
    FROM loan
    GROUP BY due_date
),
paid_by_date as (
    select 
        payment_date,
        sum(amount) as amount
    FROM reimbursement
    join loan on loan.id = loan_id
    GROUP BY payment_date
),
cumulated as (
    SELECT
        COALESCE(due_date, payment_date) as date,
        SUM(COALESCE(paid_by_date.amount, 0)) over (order by COALESCE(due_date, payment_date)) as paid,
        SUM(COALESCE(due_for_5_days_by_date.amount, 0)) over (order by COALESCE(due_date, payment_date)) as due_5d
    FROM due_for_5_days_by_date
    FULL OUTER JOIN paid_by_date on due_date = payment_date
)
select 
    DATE,
    due_5d - paid as overdue_5d
from cumulated
order by date

解释：

首先，我得到每个日期恰好 5 天的应付金额
然后，我得到每个日期支付的金额
然后我将在 1. 和 2. 获得的金额相加，得到累计到期和已付金额
然后差分我得到逾期金额

但问题是，这样做的话，按日期支付的金额还包含偿还不到 5 天的贷款。换句话说，最终查询中每个日期的支付金额都被高估了，因为它应该不包括该日期最近到期的贷款收到的金额。我想不出解决这个问题的方法。

你能想办法得到我想要的吗？

非常感谢您的帮助！

Answer 1

我刚刚找到了这种方法，但它使用交叉连接，所以不确定它能否很好地扩展我的整个数据，即使它托管在 BigQuery 上：

with all_dates as (
    select distinct payment_date as date
    from reimbursement
    union
    select distinct due_date as date
    from loan
    union
    select distinct due_date + interval '5' day as date
    from loan
), 
joined_data as (
    SELECT
        amount,
        due_date,
        payment_date
    from loan
    LEFT join reimbursement on loan.id = loan_id
)
select 
    date,
    SUM(
      CASE
        WHEN (due_date <= DATE - INTERVAL '5' day) and (payment_date > DATE or payment_date is null) then amount
        else 0
      END
    ) as overdue_5d
FROM all_dates
cross join joined_data
group by date
order by DATE

SQL 中的过期演变

Overdue evolution in SQL

sql

postgresql

aggregate-functions

window-functions

google-bigquery