一张表中, 查询学生及格和不及格人数

表结构为:
---------------------
class    name    score
班级     姓名     分数 

查询每个班级中, 及格和不及格学生的人数 
SELECT  `class`,
        SUM(CASE WHEN score>=60 THEN 1 ELSE 0 END) as gt60,
        SUM(CASE WHEN score>=60 THEN 0 ELSE 1 END) as lt60
FROM tb1
GROUP BY class

SELECT  class,
        SUM( IF(score >= 60, 1, 0) ) as gt,
        SUM( IF(score < 60, 1, 0 ) ) as lt
FROM tb1
GROUP BY class;