如何将一个SQL选择的聚合值除以另一个SQL选择的聚合值？

Question

我想计算系统与多少客户进行了通信。在该期间，在议题中，在小组中，在方案中，在渠道中以百分比形式计算。

公式很简单：

F = X / Y

位置：

X - number of clients communicated by system.

和

Y - number of clients in analizing sample.

我有数据库表INTERACTIONS。

表示例：

datetime       | Issue | Group | ProgramID | Channel | CustomerID | Outcome
---------------+-------+-------+-----------+---------+------------+--------
20181126000001 | Sale  | Loans | P-1       | SMS     | 5          | Accept  
20181126000005 | Sale  | Loans | P-1       | PUSH    | 7          | Ignore  
20181126000010 | Sale  | Loans | P-2       | SMS     | 8          | Ignore  
20181126000015 | Sale  | Loans | P-3       | PUSH    | 10         | Accept  

所以X的选择是：

SELECT 
    ISSUE, GROUP, PROGRAMID, CHANNEL, 
    COUNT(DISTINCT CUSTOMERID) AS Customers 
FROM INTERACTIONS  
GROUP BY ISSUE, GROUP, PROGRAMID, CHANNEL 
ORDER BY 1 ASC, 2 ASC, 3 ASC, 4 ASC;

Y的选择是：

SELECT COUNT(DISTINCT CUSTOMERID) AS Customers 
FROM INTERACTIONS;

如何结合这两个SQL选择并获得F = X / Y的报告？

我想得到类似这样的结果

Answer 1

SELECT 
     ISSUE, GROUP, PROGRAMID, CHANNEL, 
     COUNT(DISTINCT CUSTOMERID)/
    (SELECT COUNT(DISTINCT CUSTOMERID) FROM 
     INTERACTIONS) AS Customers 
FROM INTERACTIONS  
GROUP BY ISSUE, GROUP, PROGRAMID, CHANNEL
ORDER BY 1 ASC, 2 ASC, 3 ASC, 4 ASC 

只需将Y查询放入X查询