题解 | #列出供应商及其可供产品的数量#

select v.vend_id, count(prod_id) as prod_id
from Vendors as v left join Products as p on v.vend_id = p.vend_id
group by v.vend_id
order by v.vend_id;

用as换名时，所有长的字段都换成简短的缩写，需要统一。