13.
a. select pname
from parts as p,
suppliers as s,
catalog as c
where p.pid = c.pid and c.sid = s.sid
GROUP by s.sid having count(p.pid) = 1;
b. select sname from suppliers as s,
catalog as c,
parts as p
where c.sid = s.sid and p.color = ‘red’;
c. update catalog set cost = cost + cost .2;
d. select pname
from parts as p, suppliers as s, catalog as c
where sname = ‘Acme widget suppliers’ and p.pid = c.pid and c.sid = s.sid
15.
