将两个 COUNT 合并到一个 SQL 查询中

Question

我需要做一个查询来显示 new_customers X customers_cancellations

通过此查询，我可以按月获得 new_customers：

select count(start_date), to_char(start_date, 'MM') as monthNumber, to_char(start_date, 'YY') as yearNumber 
from customer where start_date is not null 
group by to_char(start_date, 'MM'), to_char(start_date, 'YY') 
order by yearNumber, monthNumber;

有了这个，我可以让客户按月取消订单：

select count(cancellation_date), to_char(cancellation_date, 'MM') as monthNumber, to_char(cancellation_date, 'YY') as yearNumber
from customer where cancellation_date is not null 
group by to_char(cancellation_date, 'MM'), to_char(cancellation_date, 'YY') 
order by yearNumber, monthNumber;

这两个查询 return 类似于：

count|  monthnumber |yearnumber
1    |  1           | 20
7    |  2           | 20
5    |  3           | 20

但我想要这样的东西：

customer_out_count|customer_in_count| monthnumber   |yearnumber
 0                |1                |   1           | 20
 0                |7                |   2           | 20
 1                |0                |   3           | 20
 0                |1                |   4           | 20
 5                |7                |   5           | 20
 1                |5                |   6           | 20

我已经尝试过这个查询：

select 'start' as type, count(start_date) as count, to_char(start_date, 'MM') as monthNumber, to_char(start_date, 'YY') as yearNumber
from customer where start_date is not null
group by to_char(start_date, 'MM'), to_char(start_date, 'YY')
union
select 'cancellation' as type, count(cancellation_date) as counta, to_char(cancellation_date, 'MM') as monthNumber, to_char(cancellation_date, 'YY') as yearNumber
from customer where cancellation_date is not null
group by to_char(cancellation_date, 'MM'), to_char(cancellation_date, 'YY')
order by yearNumber, monthNumber;

结果是“ok”：

type                  |newcount         | monthnumber   |yearnumber
 start                |1                |   1           | 20
 cancellation         |1                |   1           | 20
 cancellation         |7                |   2           | 20
 start                |3                |   3           | 20
 cancellation         |1                |   4           | 20
 start                |7                |   5           | 20
 start                |5                |   6           | 20

但我需要对代码进行一些操作才能实现我所需要的。

如何将这两个查询合并为一个？我正在使用 postgreslq。

Answer 1

一个选项将行反透视，然后聚合。在 Postgres 中，您可以使用横向连接来表达：

select
    sum(x.customer_in_count)  as customer_in_count,
    sum(x.customer_out_count) as customer_out_count
    to_char(x.dt, 'MM') as monthNumber, 
    to_char(x.dt, 'YY') as yearNumber
from customer c
cross join lateral (values
    (c.start_date, 1, 0), (c.cancellation_date, 0, 1)
) as x(dt, customer_in_count, customer_out_count)
where x.dt is not null
group by monthNumber, yearNumber
order by monthNumber, yearNumber

将两个 COUNT 合并到一个 SQL 查询中

merge two COUNT in one SQL query

sql

postgresql

datetime

sum

unpivot