Database: dog_kennels
Question: Tell me the owner id and last name of the owner who spent the most on treatments of his or her dogs.
SQL:
SELECT T1.owner_id ,  T1.last_name FROM Owners AS T1 JOIN Dogs AS T2 ON T1.owner_id  =  T2.owner_id JOIN Treatments AS T3 ON T2.dog_id  =  T3.dog_id GROUP BY T1.owner_id ORDER BY count(*) DESC LIMIT 1