求助 下面语句是什么意思

Declare @avg2 float;
SELECT @avg2 = AVG(Grade) FROM dbo.Grade WHERE CourseID='Dp010002' AND Semester='2'
IF @avg2 >=75
SELECT top 3 StudentName AS 学生名,Grade AS 成绩,
状态 = case
WHEN Grade>95 THEN '杰出'
WHEN Grade>69 and Grade<=95 THEN '优秀'
WHEN Grade>60 and Grade<=69 THEN '合格'
ELSE '继续努力'
END
FROM dbo.Student AS S,dbo.Grade AS G
WHERE S.StudentID = G.StudentID AND G.CourseID='Dp010002' AND G.Semester='2' ORDER BY G.Grade DESC
ELSE
SELECT top 3 StudentName AS 学生名,Grade AS 成绩,
状态 = case
WHEN Grade>60 THEN '合格'
ELSE '继续努力'
END
FROM dbo.Student AS S,dbo.Grade AS G
WHERE S.StudentID = G.StudentID AND G.CourseID='Dp010002' AND G.Semester='2' ORDER BY G.Grade