有一个test数据库,里面有一张学员表student,有三个字段,calss,name,score,分别代表班级,姓名,成绩
查询每个班级的几个人数和不及格人数,输出格式是 class,及格人数,不及格人数
select class,
(select count(*) from student where class="stu".class and score>=60) jige,
(select count(*) from student where class="stu".class and score<60) bujige
from student stu group by class
//性能上,不知道怎么样。