Postcode and PostcodeLocator difference

PL/pgSQL

SELECT count(addressbasepremium.abp_blpu_record.uprn) FROM addressbasepremium.abp_blpu_record, addressbasepremium.abp_delivery_point 
WHERE addressbasepremium.abp_blpu_record.uprn = addressbasepremium.abp_delivery_point.uprn AND
addressbasepremium.abp_blpu_record.postcode_locator != addressbasepremium.abp_delivery_point.postcode;