CREATE TABLE Company (cid int, name text);
CREATE TABLE Product (name text, price float, cid int REFERENCES Companies);

/* Return companies who only sell products less than $200 */
/* Use the EXISTS or NOT EXISTS statement */
SELECT DISTINCT C.name
FROM Company C
WHERE NOT EXISTS (SELECT P.price
                  FROM Product P
		  WHERE P.price >= 200 AND
		  C.cid = P.cid)

/* Return companies who only sell products less than $200 */
/* Use the ALL statement */
SELECT DISTINCT C.name
FROM Company C
WHERE 200 > ALL (SELECT P.price
	         FROM Product P
	         C.cid = P.cid)

/* Return companies who only sell products less than $200 */
/* Use the IN or NOT IN statement */
SELECT DISTINCT C.name
FROM Company C
WHERE C.name NOT IN (SELECT C2.name
		     FROM Product P, Company C2
		     WHERE P.pid = C.cid AND
		     P.price >= 200)
