SQL：将两个计数查询合二为一

Question

目前我有两个 sql 查询，每个查询都返回特定日期特定列的总数：

select first_name COUNT(*) as totalCount from some_table
where the_date >= '2020-09-14' and the_date <='2020-09-15' 
group by first_name

select first_name COUNT(*) as totalCount from some_table
where the_date >= '2020-09-16' and the_date <='2020-09-17' 
group by first_name

每个都会返回一个表格，例如：

first_name | totalCount

相反，我想要一个返回结果的查询：

first_name | count1 | count2

count1 是第一个查询的总计数，count2 是第二个查询的总计数

我试过了：

select first_name COUNT(*) as count1 from some_table
where the_date >= '2020-09-14' and the_date <='2020-09-15' 
group by first_name
UNION
select first_name COUNT(*) as count2 from some_table
where the_date >= '2020-09-16' and the_date <='2020-09-17' 
group by first_name

但它仍然只返回count1的结果。

Answer 1

使用条件聚合：

SELECT
    first_name,
    COUNT(*) FILTER (WHERE the_date >= '2020-09-14' AND the_date < '2020-09-15') AS totalCount1,
    COUNT(*) FILTER (WHERE the_date >= '2020-09-16' AND the_date < '2020-09-17') AS totalCount2
FROM some_table
GROUP BY
    first_name;

请注意，我使用的不等式如下所示：

the_date >= '2020-09-14' AND the_date < '2020-09-15'

这将只针对日期'2020-09-14'。

编辑：

对于您在下面的 cmets 中的后续问题，如果您想匹配两个计数均为零的名字，请使用：

SELECT
    first_name
FROM some_table
GROUP BY
    first_name
HAVING
    COUNT(*) FILTER (WHERE the_date >= '2020-09-14' AND the_date < '2020-09-15' OR
                           the_date >= '2020-09-16' AND the_date < '2020-09-17') = 0;