获取客户ID和第20次交易日期的MySQL - SQL查询

Question

我无法提出查询来获取客户 ID 列表及其第 20 次购买的日期。

我得到了一个名为 transactions 的表，其中列名为 customer_id 和purchase_date。表中的每一行都等于一笔交易。

customer_id	购买日期
1	2020-11-19
2	2022-01-01
3	2021-12-05
3	2021-12-09
3	2021-12-16

我尝试这样做，并假设我必须计算 customer_id 被提及的次数，如果计数等于 20，则返回 id 编号。

SELECT customer_id, MAX(purchase_date)
FROM transactions
(
     SELECT customer_id,
     FROM transactions
     GROUP BY customer_id
     HAVING COUNT (customer_id) =20
)

如何让它返回 customer_id 列表以及第 20 次交易的日期？

Answer 1

我的解决方案：

select *
from transactions t
inner join (
   select 
      customer_id,
      purchase_date,
      row_number() over (partition by customer_id order by purchase_date) R
   from transactions) x on x.purchase_date=t.purchase_date
                       and x.customer_id=t.customer_id
where x.R=20;

参见：DBFIDDLE

对于MySQL5.7，请参见：DBFIDDLE

set @r:=1;
select *
from transactions t
inner join (
   select 
      customer_id,
      purchase_date,
      @r:=@r+1 R
   from transactions) x on x.purchase_date=t.purchase_date
                       and x.customer_id=t.customer_id
where x.R=20;

Answer 2

您需要选择属于customer_id的交易行，并按第20行过滤结果

SELECT * FROM (
    SELECT customer_id, purchase_date, ROW_NUMBER() OVER(
        PARTITION BY customer_id
        ORDER BY purchase_date DESC
    ) AS nth
    FROM transactions
) as t WHERE nth = 20