请用多种方式查询出选了数学这门课的所有学生姓名

admin

已知学生表(student:id,name),课程表(class:id,name),选课表(sc:studentid,classid),请用多种方式查询出选了数学这门课的所有学生姓名(两种以上，并说明哪种效率最高)

moon110

select t3.name from class t1 

    left join sc t2 on t1.id=t2.classid

    left join student t3 on t2.studentid=t3.id

    where t1.name='数学'

select s.name from stutent s,class c, sc.sc

where c.name ='数学',and studentid=s.id and classid=c.id

select name from student where id in (select t2.studentid from class t1,sc t2 where t1.id=t2.classid and t1.name='数学')

m1359292934

select s.name from stutent s,class c, sc.sc

where c.name ='数学',and studentid=s.id and classid=c.id

 

 select s.name ,count(grade) from grade_test g
inner join  class_test c on c.cid=g.cid and c.name ='数学'
inner join student_test s on g.sid=s.sid
group by s.name;

第一种效率高直接从选数学课 的学生中查起