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全部文章（共86篇）

题解 | 查询培训指定课程的员工信息

SELECT t1.staff_id, t1.staff_name FROM staff_tb t1 LEFT JOIN cultivate_tb t2 ON t1.staff_id=t2.staff_id WHERE t2.course LIKE '%course3%'

2025-12-22

0 38

题解 | 统计所有课程参加培训人次

WITH t1 AS ( SELECT CASE WHEN course IS NULL THEN 0 ELSE LENGTH(course)-LENGTH(REPLACE(course,',',''))+1 ...

2025-12-21

0 31

题解 | 查询连续入住多晚的客户信息？

SELECT t2.user_id,t2.room_id,t1.room_type,DATEDIFF(t2.checkout_time,t2.checkin_time) AS days FROM guestroom_tb t1 LEFT JOIN checkin_tb t2 ON t1.room_i...

2025-12-20

0 35

题解 | 分析客户逾期情况

SELECT t2.pay_ability, CONCAT(ROUND(SUM(CASE WHEN t1.overdue_days IS NOT NULL THEN 1 ELSE 0 END)/COUNT(*)*100,1),'%') AS overdue_ratio FROM loa...

2025-12-18

0 37

题解 | 每个月Top3的周杰伦歌曲

with t as ( select MONTH(fdate) as month, row_number() over(partition by month(t1.fdate) order by count(t2.song_name) desc, t1.song_id ...

2025-12-17

0 40

题解 | 删除记录（三）

DROP TABLE IF EXISTS nowcoder_exam_record; CREATE TABLE IF NOT EXISTS nowcoder_exam_record( id int(11) PRIMARY KEY AUTO_INCREMENT COMMENT"自...

2025-06-28

0 80

题解 | 删除记录（二）

DELETE FROM exam_record WHERE submit_time IS NULL OR TIMESTAMPDIFF(MINUTE,start_time,submit_time)<5 ORDER BY start_time LIMIT 3;

2025-06-28

0 61

题解 | 删除记录（一）

DELETE FROM exam_record WHERE TIMESTAMPDIFF(MINUTE,start_time,submit_time)<5 AND score<60;

2025-06-28

0 72

题解 | 更新记录（二）

UPDATE exam_record SET submit_time="2099-01-01 00:00:00",score=0 WHERE start_time<"2021-09-01" AND submit_time IS NULL;

2025-06-28

0 66

题解 | 更新记录（一）

UPDATE examination_info SET tag="Python" WHERE tag="PYTHON";

2025-06-28

0 53