获取每个客户的ID和名称以及总金额(购买产品数量的总和)

Question

我很难处理这个JOIN+SUM查询

我有以下表格(客户、订单、产品(

client_id	名称
1	Frank
2	Emile
3	Rose
4	劳拉
5	Samuel

如果你只想要产品数量的总和：

SELECT c.client_id, c.first_name, SUM(o.units_sold)
FROM
client c
INNER JOIN orders o ON o.client_id = c.client_id
GROUP BY c.client_id, c.first_name;

但如果你也想看看价格：

SELECT c.client_id, c.first_name, SUM(o.units_sold), 
SUM(o.units_sold*p.price)
FROM
client c
INNER JOIN orders o ON o.client_id = c.client_id
INNER JOIN products p ON o.product_id = p.product_id
GROUP BY c.client_id, c.first_name;