题解 | 查询出每个品牌在特定时间段内的退货率以及平均客户满意度评分

select
    s.brand_id as brand_id,
    brand_name,
    round(sum(return_status) / count(*), 2) as return_rate_July_2024,
    round(avg (customer_satisfaction_score), 2) as average_customer_satisfaction_score
from
    sales_orders as s
    inner join brand_info as b on s.brand_id = b.brand_id
    inner join customer_feedback as c on s.order_id = c.order_id
where
    substr(order_date, 1, 7) = '2024-07'
group by
    s.brand_id
order by
    brand_id;

下午突然脑袋很晕，感觉不会写SQL了

1.这里面的平均值函数是avg，不是average

2.group by 彼此一一对应的话就不用就不用都分组了，本来想按照s.brand_id as brand_id,

brand_name,分组，其实一个就可以了

3.布尔值也可以使用sum函数