题解 | 电商平台需要对商品的销售和评价情况进行综合分析

select
    product_id,
    product_name,
    sum(quantity) as total_quantity,
    round(average_rating, 2) as average_rating
from
    sales_underline
    left join products_underline using (product_id)
    join (
        select
            product_id,
            avg(rating) as average_rating
        from
            reviews_underline
        group by
            product_id
        having
            average_rating <= 4
    ) as t using (product_id)
group by
    product_id,
    product_name
order by
    average_rating ASC,
    product_id ASC;

看了很多其他同学的解法，我真的想说，无脑联成宽表丝毫不考虑笛卡尔积还有滥用临时表，在实际大数据量情况下代码表现通常都很糟糕，不要以为系统给你过了就是对的，希望大家多多精进，少写慢sql