None
SELECT s.buyer_id
FROM Sales s
JOIN Product p
ON s.product_id = p.product_id
GROUP BY s.buyer_id
HAVING sum(p.product_name='S8')>0
AND sum(p.product_name='iPhone')=0
None
SELECT s.buyer_id
FROM Sales s
JOIN Product p
ON s.product_id = p.product_id
GROUP BY s.buyer_id
HAVING sum(p.product_name='S8')>0
AND sum(p.product_name='iPhone')=0