SQL如何计算至少有1,5,10,20等事务的信用卡数量

Question

我有一套信用卡交易数据。

create table trans (
  card_id int,
  amount int
);

insert into trans values (1, 1);
insert into trans values (2, 1);
insert into trans values (3, 1);
insert into trans values (4, 1);
insert into trans values (5, 1);
insert into trans values (5, 1);
insert into trans values (6, 1);
insert into trans values (6, 1);
insert into trans values (7, 1);
insert into trans values (7, 1);
insert into trans values (8, 1);
insert into trans values (8, 1);
insert into trans values (8, 1);
insert into trans values (9, 1);
insert into trans values (9, 1);
insert into trans values (9, 1);
insert into trans values (10, 1);
insert into trans values (10, 1);
insert into trans values (10, 1);
insert into trans values (10, 1);

我想知道：

1. how many cards were used to make at least 1 transaction
2. how many cards were used to make at least 5 transactions
3. how many cards were used to make at least 10 transactions
4. how many cards were used to make at least 20 transactions
etc...

SQL：

select count, sum(count2) from
  (
  select count, count(*) count2 from
    (
    select card_id, count(*) count
    from trans
    group by card_id 
    ) d
  group by count
  ) d2
where count> {is at least __} /*this is the part causing an error*/
group by count
order by count

您的SQL语法出现了错误.

http://sqlfiddle.com/#!9/705b5/5

Answer 1

由于组重叠，我认为条件聚合是一种更好的方法：

select sum(cnt >= 1) as trans_1,
       sum(cnt >= 5) as trans_5,
       sum(cnt >= 10) as trans_10,
       sum(cnt >= 20) as trans_20
from (select card_id, count(*) as cnt
      from trans
      group by card_id 
      ) d;