SQL 请求 : Count with group by and total to make a percentage on the same line

Question

我目前因一个简单的请求而被阻止...:

我有这个数据库:

order | couple | first | second
-------------------------------
  1   |  A-B   |   A   |   B
  2   |  A-D   |   A   |   D
  3   |  A-C   |   A   |   C
  4   |  A-B   |   A   |   B
  5   |  Y-Z   |   Y   |   Z

我想在一行中获得:

order | count | total | percentage
-------------------------------
A-B   |  2   |   4    |    50%
A-D   |  1   |   4    |    25%
A-C   |  1   |   4    |    25%
Y-Z   |  1   |   1    |    100%

我可以找到第一部分:订单 | count...但是不可能将它与总数和百分比结合起来(而不是使用子查询...):我在尝试进行结合时遇到了很多不同的错误。

我对第一部分的要求:

SELECT couple,count(couple) 
FROM DATA d1 
WHERE exists (
  SELECT * 
  FROM DATA d2 
  WHERE d1.first = d2.first) 
GROUP BY d1.couple;

我对第二部分的要求:

SELECT first, count(first) 
FROM DATA 
GROUP BY first;

有人知道提示吗？

Answer 1

我想你想要:

select couple, count(*),
       count(*) over (partition by first) as total,
       (count(*) * 1.0 / sum(count(*)) over (partition by first) ) as ratio
from t
group by couple, first;