1 统计复旦用户8月练题情况
题目
现在运营想要了解复旦大学的每个用户在8月份练习的总题目数和回答正确的题目数情况，请取出相应明细数据，对于在8月份没有练习过的用户，答题数结果返回0.
用户信息表user_profile
根据示例，你的查询应返回以下结果
示例1
输入：
drop table if exists `user_profile`;
drop table if exists `question_practice_detail`;
drop table if exists `question_detail`;
CREATE TABLE `user_profile` (
`id` int NOT NULL,
`device_id` int NOT NULL,
`gender` varchar(14) NOT NULL,
`age` int ,
`university` varchar(32) NOT NULL,
`gpa` float,
`active_days_within_30` int ,
`question_cnt` int ,
`answer_cnt` int
);
CREATE TABLE `question_practice_detail` (
`id` int NOT NULL,
`device_id` int NOT NULL,
`question_id`int NOT NULL,
`result` varchar(32) NOT NULL,
`date` date NOT NULL
);
CREATE TABLE `question_detail` (
`id` int NOT NULL,
`question_id`int NOT NULL,
`difficult_level` varchar(32) NOT NULL
);
INSERT INTO user_profile VALUES(1,2138,'male',21,'北京大学',3.4,7,2,12);
INSERT INTO user_profile VALUES(2,3214,'male',null,'复旦大学',4.0,15,5,25);
INSERT INTO user_profile VALUES(3,6543,'female',20,'北京大学',3.2,12,3,30);
INSERT INTO user_profile VALUES(4,2315,'female',23,'浙江大学',3.6,5,1,2);
INSERT INTO user_profile VALUES(5,5432,'male',25,'山东大学',3.8,20,15,70);
INSERT INTO user_profile VALUES(6,2131,'male',28,'山东大学',3.3,15,7,13);
INSERT INTO user_profile VALUES(7,4321,'male',28,'复旦大学',3.6,9,6,52);
INSERT INTO question_practice_detail VALUES(1,2138,111,'wrong','2021-05-03');
INSERT INTO question_practice_detail VALUES(2,3214,112,'wrong','2021-05-09');
INSERT INTO question_practice_detail VALUES(3,3214,113,'wrong','2021-06-15');
INSERT INTO question_practice_detail VALUES(4,6543,111,'right','2021-08-13');
INSERT INTO question_practice_detail VALUES(5,2315,115,'right','2021-08-13');
INSERT INTO question_practice_detail VALUES(6,2315,116,'right','2021-08-14');
INSERT INTO question_practice_detail VALUES(7,2315,117,'wrong','2021-08-15');
INSERT INTO question_practice_detail VALUES(8,3214,112,'wrong','2021-05-09');
INSERT INTO question_practice_detail VALUES(9,3214,113,'wrong','2021-08-15');
INSERT INTO question_practice_detail VALUES(10,6543,111,'right','2021-08-13');
INSERT INTO question_practice_detail VALUES(11,2315,115,'right','2021-08-13');
INSERT INTO question_practice_detail VALUES(12,2315,116,'right','2021-08-14');
INSERT INTO question_practice_detail VALUES(13,2315,117,'wrong','2021-08-15');
INSERT INTO question_practice_detail VALUES(14,3214,112,'wrong','2021-08-16');
INSERT INTO question_practice_detail VALUES(15,3214,113,'wrong','2021-08-18');
INSERT INTO question_practice_detail VALUES(16,6543,111,'right','2021-08-13');
INSERT INTO question_detail VALUES(1,111,'hard');
INSERT INTO question_detail VALUES(2,112,'medium');
INSERT INTO question_detail VALUES(3,113,'easy');
INSERT INTO question_detail VALUES(4,115,'easy');
INSERT INTO question_detail VALUES(5,116,'medium');
INSERT INTO question_detail VALUES(6,117,'easy');
输出：
3214|复旦大学|3|0
4321|复旦大学|0|0
题解
先分析题目
1.复旦大学的每个用户-一个用户可能练习很多题，那么可能涉及到分组
2.8月份练习-需要根据data先筛选出8月份
3.练习的总题数-统计question_id
4.回答正确的题数-先筛选result为right的，再统计question_id
需要user_profile的device_id,universuty和question_practice_detail的device_id,question_id,result,data
1.先找出复旦大学的用户8月份答题情况
SELECT *
FROM user_profile up
LEFT JOIN question_practice_detail as qpd
ON qpd.device_id = up.device_id AND MONTH(qpd.date)=8
WHERE university ='复旦大学'
/*
2|3214|male|None|复旦大学|4.000|15|5|25|15|3214|113|wrong|2021-08-18
2|3214|male|None|复旦大学|4.000|15|5|25|14|3214|112|wrong|2021-08-16
2|3214|male|None|复旦大学|4.000|15|5|25|9|3214|113|wrong|2021-08-15
7|4321|male|28|复旦大学|3.600|9|6|52|None|None|None|None|None
*/
2.根据用户数分类，统计回答问题的总数
# count(qpd.question_id)不统计空值，默认为0
SELECT up.device_id,university,count(qpd.question_id),SUM(IF(qpd.result='right',1,0))
FROM user_profile up
LEFT JOIN question_practice_detail as qpd
ON qpd.device_id = up.device_id AND MONTH(qpd.date)=8
WHERE up.university ='复旦大学'
GROUP BY up.device_id