WW在搜寻

分类

错题(1) 题解(59)

/ 注册

全部文章（共35篇）

题解 | #浙大不同难度题目的正确率#

SELECT qd.difficult_level,SUM(if(qpd.result='right',1,0))/COUNT(qpd.device_id) AS corrct_rate FROM user_profile up JOIN question_practice_detail qpd O...

Mysql

2022-01-15

0 323

题解 | #统计复旦用户8月练题情况#

SELECT up.device_id,'复旦大学',COUNT(qpd.question_id),SUM(CASE WHEN qpd.result='right' THEN 1 ELSE 0 END) FROM user_profile up LEFT JOIN question_practice...

Mysql

2022-01-15

0 318

题解 | #找出每个学校GPA最低的同学#

SELECT device_id,temp.u,temp.m FROM user_profile up, (SELECT university u,MIN(gpa) m FROM user_profile GROUP BY university ORDER BY university) temp W...

Mysql

2022-01-15

0 256

题解 | #统计每种性别的人数#

SELECT (CASE WHEN CHAR_LENGTH(profile)=18 THEN 'male' ELSE 'female' END) AS gender,COUNT(*) number FROM user_submit GROUP BY gender;#这个方法不是很保险，前提前面字符...

Mysql

2022-01-14

0 309

题解 | #计算用户的平均次日留存率#

SELECT COUNT(DISTINCT q2.device_id,q2.date) / COUNT(DISTINCT q1.device_id,q1.date) AS avg_ret FROM question_practice_detail q1 LEFT JOIN question_prac...

Mysql

2022-01-14

0 320

题解 | #计算用户8月每天的练题数量#

SELECT DISTINCT DAY(qpd.date) AS day ,COUNT(DAY(qpd.date)) AS question_cnt FROM question_practice_detail qpd WHERE MONTH(date)=8 GROUP BY day; #主要得分组

Mysql

2022-01-14

0 270

题解 | #查看不同年龄段的用户明细#

SELECT device_id,gender,(CASE WHEN age>=25 THEN '25岁及以上' WHEN age>=20 THEN '20-24岁' WHEN age>0 THEN '20岁以下' ELSE '其他' END) AS age_cut FROM...

Mysql

2022-01-14

0 225

题解 | #计算25岁以上和以下的用户数量#

SELECT (CASE WHEN age>=25 THEN '25岁及以上' ELSE '25岁以下' END) AS age_cut,COUNT(device_id) as number FROM user_profile GROUP BY age_cut;

Mysql

2022-01-14

0 339

题解 | #查找山东大学或者性别为男生的信息#

SELECT device_id,gender,age,gpa FROM user_profile WHERE university='山东大学' UNION ALL SELECT device_id,gender,age,gpa FROM user_profile WHERE gender='ma...

Mysql

2022-01-14

0 280

题解 | #统计每个用户的平均刷题数#

SELECT u.university,d.difficult_level,COUNT(qpd.question_id) / COUNT(DISTINCT u.device_id) FROM user_profile u JOIN question_practice_detail qpd ON u...

Mysql

2022-01-14

0 263