Question: Find the names of the chip models that are not used by any phone with full accreditation type.
Schema: create table chip_model (model_name varchar, chip_model varchar, accreditation_type varchar, PRIMARY KEY (model_name)); create table phone (model_name varchar, chip_model varchar, accreditation_type varchar, PRIMARY KEY (model_name))
SQL: select model_name from chip_model except select chip_model from phone where accreditation_type = 'full'