具有平均值和计数 SQL 的子查询

Question

亲爱的，我的数据包含以下信息；客户ID、交易金额和交易对手地区。对于每个地区，我想计算交易量的平均值。我的想法是使用子查询，但我坚持了下来。这是我目前的想法，不可行。

select avg(count_for_DK) from data where
(select count(amount) as count_for_DK, customer_id from data 
where country = 'DK'
group by customer_id, country 
order by customer_id asc)

有人帮帮我吗？

我的 table 示例屏幕： https://ibb.co/BZXDL4Q

Answer 1

根据我的理解，您想获得国家/地区 ='DK' 的客户明智的平均金额如果这个逻辑是你正在寻找的，那么下面的查询将起作用：

 select customer_id ,avg(amount) as average_for_DK from data 
    where country = 'DK'
    group by customer_id
    order by customer_id

如果您想获得'DK'

国家/地区的客户完成的平均交易次数

select avg(count_for_DK) from (
 select customer_id ,count(amount) as count_for_DK from data 
        where country = 'DK'
        group by customer_id
        order by customer_id) t

如果您想获得每个国家/地区的客户完成的平均交易次数：

select country,avg(count_for_country) from (
 select country,customer_id ,count(amount) as count_for_country from data 
        
        group by country,customer_id
        order by country,customer_id) t
group by country

具有平均值和计数 SQL 的子查询

Subquery with average and count in SQL

sql

count

subquery