MYSQL查询计算电子邮件的百分比不为空

Question

我有这两个查询。

计算为空的电子邮件计数

SELECT COUNT(*) as invalid_email FROM distinct_customers WHERE c_email IS NULL;

计算每封电子邮件的数量

SELECT COUNT(distinct c_number) as total FROM distinct_customers;

我正在尝试将其与查询结合起来，以便给我一定百分比的有效电子邮件（不为null）

我尝试了几种方法，但我不是mysql专家。

数学上应该是

643（空电子邮件）* 100/1292（总电子邮件）

Answer 1

SELECT AVG(c_email IS NOT NULL) as invalid_email_ratio,
       100 * AVG(c_email IS NOT NULL) as invalid_email_perentile           
FROM distinct_customers ;

Answer 2

SELECT (COUNT(case when c_email IS NULL then 1 end)*100.00)/
        COUNT(distinct c_number) as percentage
FROM distinct_customers