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题解 | #查找后多列排序#

select device_id,gpa,age from user_profile order by gpa asc,age asc # 1/3组用例通过 and改逗号，就出来了。不过不是很懂原理

2023-03-04

0 161

题解 | #查找后排序#

select device_id,age from user_profile order by age asc 在中等和困难里挣扎后，突然遇到一道入门，也太快乐了

2023-03-04

0 171

题解 | #浙大不同难度题目的正确率#

select qd.difficult_level, #正确率是答正确的题/总题数 sum(if(result='right',1,0))/count(qpd.question_id) as correct_rate from user_profile as up inner join quest...

2023-03-04

0 250

题解 | #统计复旦用户8月练题情况#

select up.device_id,up.university, count(qpd.question_id) as question_cnt, sum(if(qpd.result='right',1,0)) as right_question_cut from user_profile as ...

2023-03-04

0 185

题解 | #找出每个学校GPA最低的同学#

select device_id,university,gpa from user_profile where (university,gpa) in (select university,min(gpa) from user_profile group by university) order b...

2023-03-03

0 178

题解 | #截取出年龄#

select substring_index(substring_index(profile,',',3),',',-1) as age, count(device_id) as number from user_submit group by age 老是漏写，

2023-03-03

0 187

题解 | #提取博客URL中的用户名#

select device_id, substring_index(blog_url,'/',-1) from user_submit #group by device_id 有聚合函数的情况下才需要group by

2023-03-03

0 218

题解 | #统计每种性别的人数#

select substring_index(profile,',',-1) as gender, count(device_id) as number from user_submit group by gender group by和count（device_id)确实是没有想到的

2023-03-03

0 189

题解 | #计算用户的平均次日留存率#

select count(date2) / count(date1) as avg_ret from ( select distinct qpd.device_id, qpd.date as date1, uniq_id_date.date a...

2023-03-03

0 214

题解 | #计算用户8月每天的练题数量#

select day(date) as day, count(question_id) as question_cnt from question_practice_detail where month(date) = 8 and year(date) = 2021 group by date 一遇...

2023-03-03

0 199