按键的不同子集分组

Question

我有一张产品销售表

id  product_id  price_sold
1      1            500
2      1            300
3      2            100
4      3            200
5      3            100

我希望能够通过不同的产品子集来计算价格，比如：每组产品的价格总和1,2。并且计算每组产品2,3的价格总和，因此所需的结果将是：

group 1, 900
group 2, 400

您能以高效优雅的方式帮助实现这一目标吗？

Answer 1

做你想做的事有点挑战，因为这些组重叠。你有两个选择。第一个是进行条件聚合并将结果放在列中：

select sum(case when product_id in (1, 2) then price_sold end) as group1,
       sum(case when product_id in (2, 3) then price_sold end) as group2
from productsales ps;

要在单独的行上获得结果，您可以转动此结果。或者，您可以直接进行计算。为此，您需要构建一个描述组的表：

[注意：Stack Overflow不允许我在此答案中包含我的最终查询。它在评论中。]

编辑：由于戈登无法发表答案，我会这样做。 （我希望这对你戈登没问题。）

select pg.grpid, sum(ps.price_sold)
from productsales ps
join
(
  select 1 as grpid, 1 as product_id
  union all
  select 1 as grpid, 2 as product_id
  union all
  select 2 as grpid, 2 as product_id
  union all
  select 2 as grpid, 3 as product_id
) pg on ps.product_id = pg.product_id
group by pg.grpid;

Answer 2

SQL Fiddle：

SELECT 'GROUP 1' AS `Group`, SUM(price_sold) AS PriceSum
FROM MyTable
WHERE product_id = 1 OR product_id = 2
UNION
SELECT 'GROUP 2', SUM(price_sold)
FROM MyTable
WHERE product_id = 2 OR product_id = 3

结果如下：