使用最小日期 Postgres 计算唯一数据

Question

我在尝试计算表中的数据时遇到问题。

例如我的桌子是这样的：

table = test
id       | transaction_date
1        | '2021-10-01 00:00:00'
2        | '2021-10-01 00:00:00'
3        | '2021-10-02 00:00:00'
4        | '2021-10-03 00:00:00'
5        | '2021-10-04 00:00:00'
6        | '2021-10-05 00:00:00'
7        | '2021-10-06 00:00:00'

1        | '2021-11-01 00:00:00'
2        | '2021-11-01 00:00:00'
3        | '2021-11-02 00:00:00'

1        | '2021-12-01 00:00:00'
2        | '2021-12-01 00:00:00'
3        | '2021-12-02 00:00:00'
4        | '2021-12-03 00:00:00'
8        | '2021-12-04 00:00:00'
8        | '2021-12-05 00:00:00'
9        | '2021-12-06 00:00:00'
9        | '2021-12-07 00:00:00'

我尝试使用此查询

WITH first_transaction_AS (SELECT MIN(transaction_date), id FROM test),
previous_month AS (SELECT DISTINCT idFROM test 
WHERE transaction_date >= date_trunc('month', transaction_date)-interval '1 month' 
AND transaction_date < date_trunc('month', transaction_date)

-- WHERE clause for previous month will be dynamic

SELECT date_trunc('month', transaction_date), COUNT(DISTINCT id)
FROM test 
WHERE test.id NOT IN (SELECT id FROM previous_month) AND transaction_date NOT IN (SELECT min FROM first_transaction)

我想实现一个聚合查询，其中： 计算 ID 其中 ID 本月有交易且 ID 上个月无交易且不是 ID 的第一次交易

目前的问题是，ID 8 和 9 仍然会被计算在内，因为他们在同月的第一笔交易之后还有一笔交易。

所以我的目标是：

    Date                    |         Count
  2021-12-01 00:00:00       |           1  (4)

Answer 1

根据规则只有 1 个。

select 
  date(date_trunc('month', transaction_date)) as "Date"
, count(distinct id) as "Count"
from test t
where transaction_date >= date_trunc('month', current_date)
  and transaction_date < (date_trunc('month', current_date)+interval '1 month') 
  and not exists ( -- not previous month
      select 1
      from test t2
      where t2.id = t.id
        and t2.transaction_date >= date_trunc('month', current_date) - interval '1 month'
        and t2.transaction_date <  date_trunc('month', current_date)
  
  )
  and exists ( -- created previously
      select 1
      from test t2
      where t2.id = t.id
        and t2.transaction_date <  date_trunc('month', current_date)
  )
group by date_trunc('month', transaction_date)
  
  

日期 |数数 :--------- | ----: 2021-12-01 | 1

dbfiddle here

上的演示