1. SELECT sname, grade FROM enroll NATURAL JOIN student WHERE cno = 302;
2. SELECT dname FROM major NATURAL JOIN student WHERE age < 19 GROUP BY dname;
3. select cno, sectno from section natural join enroll group by dname, cno, sectno having count(sid) < 10;
4. select * from enroll where sid = 16;
select grade from enroll where sid = 16 and dname = 'Computer Sciences' and cno = 302 and sectno = 1;