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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(question_id)/count(distinct qpd.device_id) as avg_answer_cnt from user_profile AS up inner join question_practice_detail A...

Mysql

2021-11-05

0 342

题解 | #浙江大学用户题目回答情况#

select question_practice_detail.device_id, question_practice_detail.question_id, question_practice_detail.result FROM question_practice_detail inner ...

Mysql

2021-11-01

1 532

题解 | #分组排序练习题#

select university, //表头的University AVG(question_cnt) AS avg_question_cnt //表头的avg_question_cnt来源与平均值 FROM user_profile//不要遗漏不要遗漏不要遗漏不要遗漏不要遗漏 group by ...

Mysql

2021-11-01

2 431

题解 | #分组过滤练习题#

select university, avg(question_cnt) AS avg_question_cnt, AVG(answer_cnt) AS avg_answer_cnt FROM user_profile GROUP BY university HAVING avg(questio...

Mysql

2021-10-29

0 394

题解 | #分组计算练习题#

SELECT gender, university, //表头的性别和学校 COUNT(university) AS user_num, //用户数 ROUND(AVG(active_days_within_30),1) AS avg_active_day, //平均活跃数，保留一位小数 ROUND...

Mysql

2021-10-29

10 665

题解 | #计算男生人数以及平均GPA#

SELECT COUNT(gender) AS male_num, ROUND(AVG(gpa),1) AS avg_gpa FROM user_profile WHERE gender='male' 读题：计算人数，用count()函数，统计平均值，用avg()函数，限定男生，where语句限定...

Mysql

2021-10-28

0 609

题解 | #查找GPA最高值#

select max(gpa ) AS gpa from user_profile WHERE university='复旦大学' 另一种写法是select gpa from user_profile where university='复旦大学' order by gpa desc limit...

Mysql

2021-10-28

0 481

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%' 学会like操作符的各种用法，选取 name 包含模式 "oo" 的所有客户： SELECT * FROM Websites WHERE...

Mysql

2021-10-28

0 406

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= '复旦大学') 需要加深...

Mysql

2021-10-28

0 324

题解 | #高级操作符练习(1)#

SELECT device_id, gender, age, university, gpa from user_profile WHERE gpa>3.5 and gender = 'male' 一定要看清题目，关键条件男性和3.5以上，缺一不可，同时gender列数据类型为字符型，gpa...

Mysql

2021-10-27

0 440