Question: Which cmi cross reference id is not related to any parking taxes?
Schema: create table parking_fines (cmi_cross_ref_id varchar, PRIMARY KEY (cmi_cross_ref_id)); create table cmi_cross_references (cmi_cross_ref_id varchar, PRIMARY KEY (cmi_cross_ref_id))
SQL: select cmi_cross_ref_id from cmi_cross_references except select cmi_cross_ref_id from parking_fines