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题解 | #浙江大学用户题目回答情况#

select q.device_id,question_id,result //注意：两个表***有的字段必须：表别名.字段名指明来自那张表？ from question_practice_detail q join user_profile u on q.device_id = u.device...

Mysql

2022-03-13

1 208

题解 | #分组排序练习题#

select university,avg(question_cnt) as avg_question_cnt from user_profile group by university order by avg_question_cnt;//默认升序

Mysql

2022-03-13

0 220

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...

Mysql

2022-03-13

0 182

题解 | #分组过滤练习题#

select university, avg(question_cnt) as avg_question_cnt,//平均 avg(answer_cnt) as avg_answer_cnt//平均 from user_profile group by universit...

Mysql

2022-03-13

1 201

题解 | #分组计算练习题#

select gender, university, count(gender) user_num,//性别计数 avg(active_days_within_30) avg_active_days,//平均 avg(question_cnt) avg_question_cnt//平均 fr...

Mysql

2022-03-13

0 240

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'; 1.男性 2.计数：count() 3.平均：avg() 1.别名 2.round():...

Mysql

2022-03-13

0 224

题解 | #查询结果限制返回行数#

select device_id from user_profile limit 0,2; //limit x,y; x:起始记录的下标（第一题记录下标为0），y:共展示y条记录（包括下标为 x 的记录）

Mysql

2022-03-13

0 204

题解 | #查看学校名称中含北京的用户#

select gpa from user_profile where university = '复旦大学' order by gpa desc limit 0,1; //降序排列去第一名；limit 下标从0开始，取1条数据。

Mysql

2022-03-13

0 269

题解 | #查看学校名称中含北京的用户#

select round(max(gpa),1)//max() 求最大值。round(哪个值，小数点保留几位):四舍五入函数 from user_profile where university = '复旦大学';

Mysql

2022-03-13

10 286

题解 | #查找后多列排序#

select device_id,gpa,age from user_profile order by gpa asc,age asc; // order by gpa,age asc; 哪一列如何排，不指定如何排，默认升序 // order by gpa,age; 默认升序排列

Mysql

2022-03-13

7 626