SQL group by 来自多个表

Question

我正在使用 SQL Workbench/J 并希望创建两列“web_sales”和“app_sales”（参见案例语句），将 sales2019 和 sales2020 表中的销售数据结合起来。但是，我当前的代码仍然显示特定项目/成员组合的 2 条记录，这取决于数据是否来自 2019 或 2020 表。如何将 2019 年和 2020 年的数据合并到一条记录中（请参阅所需的输出）？存在于子查询之外的 group by 语句无法完成此操作。

select *
from (
    select id
      ,item
      ,member
      ,SUM(CASE WHEN platform = 'web' THEN revenue ELSE 0 END) AS web_sales
      ,SUM(CASE WHEN platform = 'app' THEN revenue ELSE 0 END) AS app_sales
    from sales2019
    group by id, item, member
    union
    select id
      ,item
      ,member
      ,SUM(CASE WHEN platform = 'web' THEN revenue ELSE 0 END) AS web_sales
      ,SUM(CASE WHEN platform = 'app' THEN revenue ELSE 0 END) AS app_sales
    from sales2020
    group by id, item, member) A
group by A.id, A.item, A.member 
order by A.item asc;

电流输出：

id  item    member  web_sales   app_sales
2   desk-blue   y   132.5   374.6
2   desk-blue   n   348.9   2597.9
2   desk-blue   y   753.1   2209.9
2   desk-blue   n   23.3    234.9
3   desk-brown  y   245.4   271.2
3   desk-brown  n   192.4   5295.8
3   desk-brown  n   1.6     776.5

期望的输出：

id  item    member  web_sales   app_sales
2   desk-blue   y   885.6   2584.5
2   desk-blue   n   372.2   2832.8
3   desk-brown  y   245.4   271.2
3   desk-brown  n   194.0   6072.3

Answer 1

你可以做union all之前聚合：

select id, item, member,
       SUM(CASE WHEN platform = 'web' THEN revenue ELSE 0 END) AS web_sales,
       SUM(CASE WHEN platform = 'app' THEN revenue ELSE 0 END) AS app_sales
from ((select id, item, member, platform, revenue
       from sales2019
      ) union all
      (select id, item, member, platform, revenue
       from sales2020
      ) 
     ) s
group by id, item, member