Database: warehouse_1
Question: Find the contents that are stored in both Chicago and New York.
SQL:
SELECT T1.contents FROM boxes AS T1 JOIN warehouses AS T2 ON T1.warehouse  =  T2.code WHERE T2.location  =  'Chicago' INTERSECT SELECT T1.contents FROM boxes AS T1 JOIN warehouses AS T2 ON T1.warehouse  =  T2.code WHERE T2.location  =  'New York'