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题解 | #统计复旦用户8月练题情况#

select device_id,university,count(question_id) ques_count, count(if(result = 'right','right',null)) right_count from( select up.device_id, up.univers...

2023-11-16

0 106

题解 | #计算25岁以上和以下的用户数量#

select case when age is null OR age < 25 then '25岁以下' when age >= 25 then '25岁及以上' end as age_cut, count(ifnull(age,0)) from user_profile grou...

2023-11-15

0 93

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 g...

2023-11-15

0 84

题解 | #统计每个用户的平均刷题数#

select up.university, qd.difficult_level, count(qpd.question_id)/count(distinct up.device_id) avg_cnt from user_profile up inner join question_prac...

2023-11-15

0 91

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, count(qpd.question_id)/count(distinct up.device_id) avg_answer_cnt from user_profile up inner join questi...

2023-11-15

0 96

题解 | #统计每个学校的答过题的用户的平均答题数#

select up.university, count(qpd.question_id) / count(distinct up.device_id) avg_answer_cnt from user_profile up inner join question_practice_detail qp...

2023-11-15

0 100

题解 | #分组过滤练习题#

select university, avg(question_cnt) avg_question_cnt, avg(answer_cnt) avg_answer_cnt from user_profile group by university having...

2023-11-15

0 78

题解 | #分组计算练习题#

select gender, university, count(id) user_num, avg(active_days_within_30), avg(question_cnt) from user_profile group by gender, university 根据性别(gender...

2023-11-15

0 76

题解 | #出现三次以上相同积分的情况#

学习新知识点replace replace(object,serch,replace) 将object中的serch替换为replace 本题中使用replace将emp_no字段中的10001替换为10005,条件是id=5

MySQL where replace update set

2021-07-14

0 346

题解 | #考试分数(二)#

查询的是所在职业分数大于该职业平均分的成绩信息首先,查询出各个职业及其平均分,作为t2表,使用grade表通过job连接t2加上条件,即t1.job = t2.job and t1.score > t2.avg_score最后对id升序select t1.id,t1.job,t1.scoref...

MySQL orderBy groupBy avg join

2021-07-13

1 337