题解 | #浙江大学用户题目回答情况#

# 方法一 全连接
 select
     q.device_id,
     question_id,
     result
 from
     question_practice_detail as q,
     user_profile as u
 where
     q.device_id = u.device_id
     and u.university = '浙江大学';

#方法二 子查询
 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'
     )

# 方法三 内连接
select q.device_id, 
    question_id,
    result
from question_practice_detail q
    INNER JOIN user_profile u
    on q.device_id = u.device_id and university = '浙江大学'

易错点：在select时，当有重复列时，要指定表的列，不然报ambiguous的错误