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题解 SQL17 平均活跃天数和月活人数

-- 交卷行为 submit_time 不为空 -- 每个月按照 month(date) 分组 -- 选出： 2021 活跃用户where submirt_time is not null andf year(submit_time)='2021' -- 获取用户活跃的日期去重 ...

Mysql

2022-02-14

0 417

题解 | #浙大不同难度题目的正确率#

SELECT rt.tag,rt.difficulty, ROUND((sum(score) -max(score) -min(score))/ (count(score)-2),1) as clip_avg_score from exam_record er join e...

Mysql

2022-02-14

0 288

题解 | #计算25岁以上和以下的用户数量#

select '25岁以下' as age_cut , count(device_id) as number from user_profile where age <25 OR age is null union all select '25岁及以上' as ...

Mysql

2022-02-06

0 412

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...

Mysql

2022-02-06

0 252

题解 | #统计每个学校的答过题的用户的平均答题数#

select u.university , count(q.question_id)/count(DISTINCT q.device_id) from question_practice_detail q inner join user_profile u where q.devi...

Mysql

2022-02-06

0 317

题解 | #最小#

-- select job|avg(1.0*score) from grade group by job ; select job , round((1.0*sum(score)/count(id) ),3) as a from grade group by job ord...

Mysql

2022-02-06

1 339

题解 | #SQL5# 左连接

select e.last_name,e.first_name,d.dept_no from employees e left join dept_emp d on e.emp_no =d.emp_no

Mysql

2021-10-06

1 347

题解 SQ3

-- select job|avg(1.0*score) from grade group by job ; select job , round((1.0*sum(score)/count(id) ),3) as a from grade group by job ord...

Mysql

2021-10-06

0 363

题解 | #考试分数(一)#

-- select job|avg(1.0*score) from grade group by job ; select job , round((1.0*sum(score)/count(id) ),3) as a from grade group by job ord...

Mysql

2021-10-02

0 379

题解 | #考试分数(一)#

先按照job 分组然后统计每个分组的求和除以统计个数、然后保留小数3位。再按照平均分排序 -- select job|avg(1.0*score) from grade group by job ; select job , round((1.0*sum(score)/c...

Mysql

2021-10-02

0 364