一、多表查询
1、子查询
1.1、SQL21 浙江大学用户题目回答情况
描述
题目：现在运营想要查看所有来自浙江大学的用户题目回答明细情况，请你取出相应数据
示例1
输入： drop table if exists `user_profile`; drop table if exists `question_practice_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 ); 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'); INSERT INTO question_practice_detail VALUES(2,3214,112,'wrong'); INSERT INTO question_practice_detail VALUES(3,3214,113,'wrong'); INSERT INTO question_practice_detail VALUES(4,6543,111,'right'); INSERT INTO question_practice_detail VALUES(5,2315,115,'right'); INSERT INTO question_practice_detail VALUES(6,2315,116,'right'); INSERT INTO question_practice_detail VALUES(7,2315,117,'wrong'); INSERT INTO question_practice_detail VALUES(8,5432,118,'wrong'); INSERT INTO question_practice_detail VALUES(9,5432,112,'wrong'); INSERT INTO question_practice_detail VALUES(10,2131,114,'right'); INSERT INTO question_practice_detail VALUES(11,5432,113,'wrong'); 输出： 2315|115|right 2315|116|right 2315|117|wrong
1.1.1、SQL语句（第一种写法）
select q.device_id, q.question_id, q.result from question_practice_detail q, user_profile u where q.device_id = u.device_id and university = '浙江大学' order by q.question_id asc
1.1.2、SQL语句（第二种写法）
select q.device_id, q.question_id, q.result from question_practice_detail q join user_profile u on q.device_id = u.device_id and university = '浙江大学' order by q.question_id asc
1.1.3、SQL语句（第三种写法）
select device_id, question_id, result from question_practice_detail where device_id in ( select device_id from user_profile where university = '浙江大学' ) order by question_id asc
