Database: dog_kennels
Question: Find the owner id and zip code of the owner who spent the most money in total for his or her dogs.
SQL:
SELECT T1.owner_id ,  T1.zip_code 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 sum(T3.cost_of_treatment) DESC LIMIT 1