What are all the different zip codes that have a maximum dew point that was always below 70?
SELECT DISTINCT zip_code FROM weather EXCEPT SELECT DISTINCT zip_code FROM weather WHERE max_dew_point_f  >=  70
SELECT DISTINCT zip_code FROM weather EXCEPT SELECT DISTINCT zip_code FROM weather WHERE max_dew_point_f  >=  70
[{'zip_code': 94063}, {'zip_code': 94107}, {'zip_code': 95113}]