如果对于每个客户，您想要最常用于接受，存款交易的货币，那么可以使用聚合和窗口函数：
select cc.*
from (select t.customerid, t.currency, count(*) as cnt,
row_number() over (partition by t.customerid order by count(*) desc) as seqnum
from transactions t
where t.function = 'DEPOSIT' and
t.status = 'ACCEPTED'
group by t.customerid, t.currency
) cc
where seqnum = 1;
编辑：
对于问题的修订解释，只需使用交叉联接：
select t.customerid, t.currency, count(*) as cnt,
tt.currency as most_popular_currency
from transactions t cross join
(select t.currency
from transactions t
where t.function = 'DEPOSIT' and
t.status = 'ACCEPTED'
group by t.currency
order by count(*) desc
limit 1
) tt
where t.function = 'DEPOSIT' and
t.status = 'ACCEPTED'
group by t.customerid, t.currency
感谢您的回覆。我希望为所有客户显示总体最受欢迎的货币。因此，换句话说，所有列都将相同。如果总体上欧元是最受欢迎的，那么所有客户的max_curr列将为EUR