SQLserver 分组排序如何优化？

Question

有个学生表 ， 存放每名学生每个月的语数英三科的成绩；
CREATE TABLE Student
(
Sid nvarchar(32) NOT NULL,
Sname nvarchar(32) NOT NULL,
Month datetime NULL,

Chinese_Score numeric(7, 2) NULL,
Math_Score numeric(7, 2) NULL,
English_Score numeric(7, 2) NULL
)
要取有这张表中， 连续两个月有同一科成绩都大于90分的学生。 由于学生表数据较大， 考虑用 lag 或 lead 函数做， 但是效率偏低。

麻烦各位大神看看有什么好的方法，帮忙解答下！！

Answer 1

select t1.sname
from student t1, student t2
where t1.sid = t2.sid and t1.month + 1 = t2.month
and t1.chinese_score > 90 and t2.chinese_score > 90
union
select t1.sname
from student t1, student t2
where t1.sid = t2.sid and t1.month + 1 = t2.month
and t1.math_score > 90 and t2.math_score > 90
union
select t1.sname
from student t1, student t2
where t1.sid = t2.sid and t1.month + 1 = t2.month
and t1.english_score > 90 and t2.english_score > 90