冷凡社长

分类

题解(2)

/ 注册

TA的专栏 0篇文章 0人订阅

0篇文章 0人学习

全部文章（共133篇）

题解 | #统计每个学校的答过题的用户的平均答题数#

select t.university,round(avg(num),4) as avg_answer_cnt from -- 思路先求出每个用户答题数 (select device_id,count(*) as num from question_practice...

Mysql

2022-07-14

0 269

题解 | #浙江大学用户题目回答情况#

select device_id,question_id,result from question_practice_detail where device_id in (select device_id from user_profile where unive...

Mysql

2022-07-14

4 224

题解 | #分组排序练习题#

select university,round(avg(question_cnt),4) as avg_question_cnt from user_profile group by university order by avg_question_cnt 主要考察排序的用法。排序默认是升序 asc...

Mysql

2022-07-14

0 231

题解 | #分组过滤练习题#

select university ,round(avg(question_cnt),3) as avg_question_cnt ,round(avg(answer_cnt),3) as avg_answer_cnt from user_profile group by university ...

Mysql

2022-07-14

0 230

题解 | #分组计算练习题#

select gender,university ,count(device_id) as user_num ,round(avg(active_days_within_30),1) as avg_active_day ,round(avg(question_cnt),1) as avg_quest...

Mysql

2022-07-14

0 168

题解 | #分组计算练习题#

select gender,university ,count(device_id) as user_num ,round(avg(active_days_within_30),1) as avg_active_day ,round(avg(question_cnt),1) as avg_quest...

Mysql

2022-07-14

0 202

题解 | #计算男生人数以及平均GPA#

select count(distinct device_id) as male_num ,avg(gpa) as avg_gpa from user_profile where gender = "male" 这个题主要是考察聚合函数的使用，这里为了避免人数出现重复，所以加入了...

Mysql

2022-07-14

1 243

题解 | #查找GPA最高值#

select max(gpa) as gpa from user_profile where university = "复旦大学" 求最值是SQL中非常经典的问题，不过这道题最让显示最大的gpa，没有别的信息那么使用 max()是最简单的。记住不要忘记条件加上复旦大学，且列名...

Mysql

2022-07-14

0 203

题解 | #查看学校名称中含北京的用户#

select device_id,age,university from user_profile where university like "%北京%" 这里主要是考察like的用法，主要是记住%%的意思，%代表一个或多个字符。一般都加在字符前后面。北京%即为从以北京为开...

Mysql

2022-07-14

0 203

题解 | #操作符混合运用#

select device_id,gender,age,university,gpa from user_profile where (gpa > 3.5 and university = "山东大学") or (gpa > 3.8 and university = ...

Mysql

2022-07-14

0 190