sql 查询及格率优秀率

表结构
stu_id varchar2(8)
stu_na varchar2(20)
stu_sco number
stu_class varchar2(4)

请用SQL语句完成如下查询：
①，求出各班的及格率（成绩>=60)
②，求出个班的优秀率（成绩>=80)

相关脚本
SELECT STU_CLASS,
ROUND(COUNT(CASE
WHEN T.STU_SCO >= 60 THEN
1
ELSE
NULL
END) * 100 / COUNT(*),
2) || ‘%’
FROM TEST_TU T
GROUP BY STU_CLASS