Joneln

分类

专题(8) 题解(77)

/ 注册

TA的专栏 85篇文章 0人订阅

MySQL试题答案解析

77篇文章 7380人学习

MySQL专题学习

8篇文章 360人学习

全部文章（共83篇）

日期函数来自专栏

Mysql

2021-11-21

0 283

窗口函数来自专栏

Mysql

2021-11-21

0 360

题解 | #计算用户8月每天的练题数量# 来自专栏

提取日期 select day(date) as day, count(question_id) as question_cnt from question_practice_detail where date like '2021-08%' group by day; day()

Mysql

2021-11-21

0 334

题解 | #查看不同年龄段的用户明细# 来自专栏

解法一 select device_id, gender, (case when age<20 then '20岁以下' when age>=20 and age<25 then '20-24岁' when age>=25 then '25岁及以上...

Mysql Mysql

2021-11-21

0 356

题解 | #计算25岁以上和以下的用户数量# 来自专栏

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

Mysql

2021-11-21

0 272

题解 | #查找山东大学男生的GPA# 来自专栏

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...

Mysql

2021-11-21

0 380

题解 | #查看学校名称中含北京的用户# 来自专栏

select device_id, age, university from user_profile where university like '%北京%'; 好久没有用过通配符了，有点手生。

Mysql

2021-11-20

0 467

题解 | #21年8月份练题总数# 来自专栏

select count(distinct device_id) as did_cnt, count( question_id) as question_cnt from question_practice_detail where date >= '2021-08-01' and date ...

Mysql

2021-11-20

0 326

题解 | #汇总各个部门当前员工的title类型的分配数目# 来自专栏

/*select d.dept_no, dept_name, title, count from departments as d right outer join (select dept_no, title, count(title) as count from titles as t left...

Mysql

2021-11-20

0 329

题解 | #牛客每个人最近的登录日期(六)# 来自专栏

select name as u_n,date, sum(number) over(partition by user_id order by date) as ps_num from passing_number p left join user u on p.user_id=u.id order...

Mysql

2021-11-19

0 403