正确的答案是2楼和7楼 不过我想要确切的subject,所以是7楼的最正确,2楼的将*改为subject,那就和7楼搜的结果一样 但2楼的速度比7楼的要快0.0003秒 SELECT subject FROM db_subject WHERE department = (SELECT department FROM db_stu_info WHERE name = '$name' select subject from db_stu_info a, db_subject b where a.department=b.department and a.name='$name'
select a.subject from db_stu_info as a left join db_subject as b on a.name=b.name and a.department=b.department where a.name='$name'
select subject from sb_subject where department=(select department from db_stu_info where name=$name)
但2楼的速度比7楼的要快0.0003秒
但2楼的速度比7楼的要快0.0003秒
SELECT subject FROM db_subject WHERE department = (SELECT department FROM db_stu_info WHERE name = '$name'
select subject from db_stu_info a, db_subject b where a.department=b.department and a.name='$name'