人生苦短，但求成长

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题解 | #截取出年龄#

select substring_index(substring_index(profile, ',', -2), ',', 1) as age, count(1) as number from user_submit group by age

Mysql Oracle

2022-03-12

2 328

题解 | #提取博客URL中的用户名#

select device_id, substring_index(blog_url, '/', -1) as user_name from user_submit

Mysql

2022-03-12

1 261

题解 | #查看不同年龄段的用户明细#

select substring_index(PROFILE, ',', -1) as gender, count(1) as number from user_submit group by gender

Mysql

2022-03-12

2 240

题解 | #查看不同年龄段的用户明细#题意不清，给的例子也不全

SELECT count(distinct q2.device_id,q2.date)/count(distinct q1.device_id,q1.date) as avg_ret FROM question_practice_detail as q1 left outer join questi...

Mysql

2022-03-12

2 240

题解 | #查看不同年龄段的用户明细#

select day(date) as day, count(question_id) as question_cnt from question_practice_detail where month(date) = '8' group by day

Mysql

2022-03-12

1 283

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...

Mysql

2022-03-12

1 264

题解 | #计算25岁以上和以下的用户数量#

select if(age >= 25,'25岁及以上','25岁以下') as age_cut, count(1) &nb...

Mysql

2022-03-12

5 338

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 =...

Mysql

2022-03-12

1 258

题解 | #统计每个用户的平均刷题数#

select t1.university,t3.difficult_level, round(count(t2.question_id)/count(distinct t1.device_id),4) as avg_answer_cnt from user_profile t1 jo...

Mysql

2022-03-12

1 264

题解 | #统计每个学校各难度的用户平均刷题数#

select t1.university,t3.difficult_level, round(count(1)/count(distinct t1.device_id),4) as avg_answer_cnt from user_profile t1 join question_pr...

Mysql

2022-03-11

1 0