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题解(26)

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全部文章（共216篇）

题解 | 提取博客URL中的用户名

SELECT device_id,SUBSTRING_INDEX(blog_url,"/",-1) user_name FROM user_submit

2025-07-21

0 23

题解 | 计算用户的平均次日留存率

不会写，抄答案了qwq@烤点老白薯(637174235)这题好难不会写[牛泪] SELECT COUNT(distinct q2.device_id,q2.date)/count(DISTINCT q1.device_id,q1.date) as avg_ret from question_prac...

2025-07-21

1 141

题解 | 计算用户8月每天的练题数量

select day(date) as day,count(1) question_cnt from question_practice_detail where date >= '2021-08-01' and date < '2021-09-01' group by day

2025-07-21

0 22

题解 | 查看不同年龄段的用户明细

select device_id,gender, (case when age < 20 then '20岁以下' when age>=20 and age<= 24 then '20-24岁' when age>= 25 then '25岁及以上' else '其他' en...

2025-07-21

0 31

题解 | 计算25岁以上和以下的用户数量

select (case when age is null then '25岁以下' when age < 25 then '25岁以下' else '25岁及以上' end) age_cut,count(*) number from user_profile group by age_cut

2025-07-21

0 25

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 =...

2025-07-21

0 23

题解 | 统计每个用户的平均刷题数

select up.university,qd.difficult_level, round(count(qd.question_id)/count(distinct qpd.device_id),4)avg_answer_cnt from (select * from user_profile w...

2025-07-21

0 31

题解 | 统计每个学校各难度的用户平均刷题数

select up.university,qd.difficult_level, round(count(qd.question_id)/count(distinct qpd.device_id),4)avg_answer_cnt from user_profile up join question...

2025-07-21

0 25

题解 | 基本数学函数

select id,value,abs(value) absolute_value,ceil(value) ceiling_value,floor(value) floor_value,round(value,1) rounded_value from numbers

2025-07-21

0 22

题解 | 纠错4

做完了SQL必知必会：）@烤点老白薯(637174235) SELECT cust_name, cust_contact, cust_email FROM Customers WHERE cust_state = 'MI' UNION SELECT cust_name, cust_conta...

2025-07-21

1 29