แดนมีเพื่อนกี่คน?ไม่จำเป็นต้องใช้โต๊ะทั้งหมด
How many friends does Dan have?It is not neccessary to use all the tables.
 PersonFriend:  (friend [ VARCHAR ] name [ VARCHAR) ]
SELECT COUNT(T2.friend) FROM Person AS T1 JOIN PersonFriend AS T2 ON T1.name = T2.name WHERE T1.name = 'Dan'