查询选修1号课程和3号课程的学生的学号;
SELECT Sno
FROM SC t
WHERE EXISTS (SELECT 1 FROM SC WHERE Cno=2 and t.Sno = Sno)
询年龄在20到35岁之间的学生的学号,姓名,系别
SELECT Sno, Sname, Sdept
FROM STUDENT
WHERE Sage between 20 and 35
查询每个学生的最高成绩
SELECT STUDENT.Sno, max(SC.Grade)
FROM STUDENT LEFT JOIN SC
ON STUDENT.Sno = SC.Sno
group by STUDENT.Sno
查询计算机系年龄不大于20岁的学生
SELECT *
FROM STUDENT WHERE Sdept = '计算机系' AND age <= 20
作业?