select device_id,gender,age,gpa
from user_profile
where university = '山东大学'
union all
select device_id,gender,age,gpa
from user_profile
where gender = 'male';
1.分别查看:union(默认去重)
2.不去重:union all
select device_id,gender,age,gpa
from user_profile
where university = '山东大学'
union all
select device_id,gender,age,gpa
from user_profile
where gender = 'male';
1.分别查看:union(默认去重)
2.不去重:union all