Mysql Select 对最后三个记录求和

Question

我有 table 字段客户日期和金额我想按日期汇总除每个客户的最后两个金额外按客户分组的金额样本数据

 customer     date               amount
  a           2020-10-1             100
  a           2020-10-2             150
  a           2020-10-3             30
  a           2020-10-4             20
  b           2020-10-1             1
  b           2020-10-5             13
  b           2020-10-7             50
  b           2020-10-9             18

想要的结果

  Customer    Amount
   A          150
   B           14

类似

select Customer , 
SUM(amount- last 2 amount)
From TableA
Group By Customer

Answer 1

一个选项使用 window 函数，在 MySQL 8.0 中可用：

select customer, sum(amount) total_amount
from (
    select a.*, row_number() over(partition by customer order by date desc) rn
    from tablea a
) a
where rn > 2
group by customer

在早期版本中，替代方法使用相关子查询 returns 每个客户的第三个最新日期进行过滤：

select customer, sum(amount) total_amount
from tablea a
where date <= (select a1.date from tablea a1 where a1.customer = a.customer order by a1.date desc limit 2, 1)
group by customer

Mysql Select 对最后三个记录求和

Mysql Select Sum but last three records

mysql

sql

sum

greatest-n-per-group

sql-limit