题解 | #列出供应商及其可供产品的数量#
列出供应商及其可供产品的数量
https://www.nowcoder.com/practice/17f22851cf204019b51a36761a3afc79
SELECT v.vend_id, COUNT(prod_id) AS prod_id FROM Vendors v LEFT JOIN Products p ON v.vend_id = p.vend_id GROUP BY v.vend_id ORDER BY v.vend_id ASC # 产品个数，计数的是prod_id，不是vend_id
