题解 | Products 表中产品名称以及对应的销售总数

select
    prod_name,
    quant_sold
from
    (
        select
            prod_id,
            sum(quantity) as quant_sold
        from
            OrderItems
        group by
            prod_id
    ) t1
    left join Products p on p.prod_id = t1.prod_id

先从OrderItems表中计算出每个prod_id对应的数量和，然后左连接到Products找name

发现自己只会用左连接TAT