将两个 SQL 查询合并为一个 SQL 查询语句

问题描述

我使用此查询来获取出生日期在给定日期范围内的用户数。

select 
    count(distinct first_name) 
from 
    quser q 
inner join 
    other_details o on o.country = q.country_of_birth 
where 
    date_of_birth between '2020-02-01' and '2020-03-01' 
    and email is not null; 

输出

 count
-------
    21
(1 row)

使用相同的查询，但是这一次，用户不在给定的范围内添加不之前介于两者之间。

select 
    count(distinct first_name) 
from 
    quser q 
inner join 
    other_details o on o.country = q.country_of_birth 
where 
    date_of_birth not between '2020-02-01' and '2020-03-01' 
    and email is not null;

输出

 count
-------
   498
(1 row)

有什么方法可以组合查询并生成单个输出，

 count no  count yes
---------  -------
   498        21
(1 row)

解决方法

使用条件聚合：

select count(distinct case when date_of_birth between '2020-02-01' and '2020-03-01' then first_name end) count_yes,count(distinct case when date_of_birth not between '2020-02-01' and '2020-03-01' then first_name end) count_no
from quser q inner join other_details o 
on o.country = q.country_of_birth 
where email is not null;