#嵌套

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#连表查询

select t1.device_id,t1.question_id,result

from question_practice_detail as t1,user_profile as t2

where t1.device_id=t2.device_id and university='浙江大学'

order by question_id

#左外连接查询select t1.device_id,question_id,resultfrom question_practice_detail as t1left join user_profile as t2on t1.device_id=t2.device_idwhere university='浙江大学'