JJJENNN

分类

/ 注册

全部文章（共38篇）

题解 | 统计各岗位员工平均工作时长

SELECT st.post, ROUND(AVG(TIMESTAMPDIFF(second,first_clockin,last_clockin)/3600),3) AS work_hours FROM staff_tb st JOIN attendent_tb at USING ...

2026-02-13

0 33

题解 | 每个商品的销售总额

SELECT p.name AS product_name, SUM(o.quantity) AS total_sales, RANK() OVER(partition by p.category order by SUM(o.quantity) DESC) AS categ...

2026-02-10

0 27

题解 | 推荐内容准确的用户平均评分

SELECT ROUND(AVG(score),3) AS avg_score FROM user_action_tb WHERE user_id IN ( SELECT DISTINCT user_id FROM recommend_tb rt JOIN user_a...

2026-02-10

0 34

题解 | 查询培训指定课程的员工信息

SELECT staff_id, staff_name FROM staff_tb st JOIN cultivate_tb ct USING (staff_id) WHERE ct.course LIKE "%course3%"

2026-02-10

0 24

题解 | 统计所有课程参加培训人次

SELECT SUM( CASE WHEN length(course) = 7 THEN 1 WHEN length(course) = 15 THEN 2 WHEN length(course) = ...

2026-02-10

0 24

题解 | 查询连续入住多晚的客户信息？

SELECT ct.user_id, ct.room_id, gt.room_type, DATEDIFF(ct.checkout_time, ct.checkin_time) AS days FROM checkin_tb ct JOIN guest...

2026-02-09

0 28

题解 | 获取指定客户每月的消费额

SELECT DATE_FORMAT(t.t_time, '%Y-%m') AS time, ROUND(SUM(t.t_amount),1) AS total FROM trade t JOIN customer c ON t.t_cus = c.c_id WHERE c.c_id = ...

2026-02-09

0 31

题解 | 获取指定客户每月的消费额

SELECT DATE_FORMAT(t.t_time, '%Y-%m') AS time, ROUND(SUM(t.t_amount),1) AS total FROM trade t JOIN customer c ON t.t_cus = c.c_id WHERE c.c_id = ...

2026-02-09

0 24