题解 | 统计快递运输时长

SELECT
    a.exp_type,
    ROUND(AVG(TIMESTAMPDIFF(SECOND,b.out_time,b.in_time) / 3600),1) AS time
FROM express_tb AS a
INNER JOIN exp_action_tb AS b
    ON a.exp_number = b.exp_number
GROUP BY a.exp_type
ORDER BY time;