CREATE TABLE phone (model_name VARCHAR2, chip_model VARCHAR2, Accreditation_type VARCHAR2)
CREATE TABLE chip_model (model_name VARCHAR2, chip_model VARCHAR2, Accreditation_type VARCHAR2)

Find the names of the chip models that are not used by any phone with full accreditation type.
SELECT model_name FROM chip_model EXCEPT SELECT chip_model FROM phone WHERE Accreditation_type = 'Full'
SELECT "model_name" FROM "chip_model" EXCEPT SELECT "chip_model" FROM "phone" WHERE "Accreditation_type" = 'Full'