题解 | 电商平台需要对各行业销售情况综合评估

select industry,
       sum(sale_amount) as 'total_sales_amount'
from merchants_underline mu
         inner join sales_underline su on mu.merchant_id = su.merchant_id
group by industry
order by total_sales_amount desc

首先对于两个表采用 inner join 进行内连接

select *
from merchants_underline mu
         inner join sales_underline su on mu.merchant_id = su.merchant_id

然后采用分组 group by,使用聚合函数sum进行求值，最后order by排序输出