1) Find students information who take a course in autumn and the teacher from ¡®cs¡¯

Select students.sid,name,students.dept,age
From sc, courses, teachers, students
Where sc.cid=courses.cid and sc.sid=students.sid and sc.teacher=teachers.teacher and courses.spring=0 and teachers.dept=¡®cs¡¯;

2)Find the average grade for each dept and each course

Select dept,cid, avg(grade)
From sc natural join students
Group by dept,cid;

3)Roll up to find the average grade for each course 
Select cid, avg(grade)
From sc
Group by cid;

4)Find the average grade for each dept.Drill down to see each students, 
Select dept,avg(grade)
From sc natural join students
Group by dept;

Select dept,sid,avg(grade)
From sc natural join students
Group by dept,sid;

5)Find the average grade for each dept. slicing on course ¡®C++¡¯;
Select dept, avg(grade) as avgOfCplus
From sc natural join students
Where cid=5
Group by dept;