题解 | 电商平台需要对商家的销售业绩、退款情况和客户满意度进行综合评估

select
        mu.merchant_id,
        mu.merchant_name,
        a.total_sales_amount,
        b.total_refund_amount,
        c.average_satisfaction_score
from 
        merchants_underline as mu
left join (
    select
        merchant_id,
        sum(sale_amount) as total_sales_amount
    from 
            sales_underline 
    group by 
            merchant_id
)a
on 
        mu.merchant_id = a.merchant_id
left join (
    select
        merchant_id,
        sum(refund_amount) as total_refund_amount
    from 
            refunds_underline 
    group by 
            merchant_id
)b
on 
        mu.merchant_id = b.merchant_id
left join (
    select
        merchant_id,
        round(avg(satisfaction_score),2) as average_satisfaction_score
    from 
            satisfaction_underline 
    group by 
            merchant_id
)c
on 
        mu.merchant_id = c.merchant_id
order by 
        mu.merchant_id