select a.product_line,b.region,b.channel_name,
sum(c.sale_amount) as total_sale_amount,
count(*) as total_sale_quantity
from oppo_products a join sales_data c using(product_id)
join sales_channels b using(channel_id)
group by a.product_line,b.region,b.channel_name,b.channel_id
order by a.product_line,b.channel_id

注意：group by 后面一定要加channel_id分组，若channel_name一样，但channel_id不同，就不会被划分到一组计算。