SELECT DISTINCT a.courier_id,b.courier_name,
b.base_salary + sum(a.delivery_fee) OVER (PARTITION BY courier_id) AS total_income
FROM deliveries_info AS a 
JOIN couriers_info AS b ON a.courier_id = b.courier_id
WHERE MONTH(a.delivery_date) = '7'
ORDER BY courier_id ASC

此题ez，两表相连之后用WHERE语句筛选出七月的快递单,然后用sum函数计算派送费用总和和基础工资相加就是总收入,最后使用ORDER BY排序输出就好了