分组之后再筛选的题目

每天录入十条成绩筛选出每天录入最高的两门成绩

结果：

代码：

CREATE TABLE StudentGrade(
stuId CHAR(4),    
subId INT,        
grade INT,       
PRIMARY KEY (stuId,subId)
)

INSERT INTO StudentGrade(stuId,subId,grade) VALUES('001',1,97);
INSERT INTO StudentGrade(stuId,subId,grade) VALUES('001',2,50);
INSERT INTO StudentGrade(stuId,subId,grade) VALUES('001',3,70);
INSERT INTO StudentGrade(stuId,subId,grade) VALUES('002',1,92);
INSERT INTO StudentGrade(stuId,subId,grade) VALUES('002',2,80);
INSERT INTO StudentGrade(stuId,subId,grade) VALUES('002',3,30);
INSERT INTO StudentGrade(stuId,subId,grade) VALUES('003',1,93);
INSERT INTO StudentGrade(stuId,subId,grade) VALUES('003',2,95);
INSERT INTO StudentGrade(stuId,subId,grade) VALUES('003',3,85);
INSERT INTO StudentGrade(stuId,subId,grade) VALUES('004',1,73);
INSERT INTO StudentGrade(stuId,subId,grade) VALUES('004',2,78);
INSERT INTO StudentGrade(stuId,subId,grade) VALUES('004',3,87);


select * from StudentGrade t
where (select count(1) from StudentGrade where subid=t.subid and grade>t.grade)<=1
order by subId,grade desc