SQL 选择多个总和?

问题描述

假设我有一张桌子:

SELECT  SUM(quantity) AS items_sold_since_date,
        product_ID
FROM    Sales
WHERE order_date >= '01/01/09'
GROUP BY product_ID

这将返回一个产品列表，其中包含自特定日期以来的销售数量.有没有办法不仅选择这个总和，而且还选择没有 where 条件的总和?我想查看自特定日期以来每种产品的销售额以及所有(不受日期限制的)销售额.

This returns a list of products with the quantity sold since a particular date. Is there a way to select not only this sum, but ALSO the sum WITHOUT the where condition? I'd like to see sales since a particular date for each product alongside all (not date limited) sales.

推荐答案

SELECT  SUM(CASE WHEN order_date >= '01/01/09' THEN quantity ELSE 0 END) AS items_sold_since_date,
        SUM(quantity) AS items_sold_total,
        product_ID
FROM    Sales
GROUP BY product_ID

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