DataBase System K Mathematical Relations a The current values( relation instance,关系实例) of a relation are specified by a table E An element t of ris a tuple(T-a), represented by a row in a table H Order of tuples is irrelevant(元组是无序的 tuples may be stored in an arbitrary order) attributes (or columns) customer_namecustomer_street customer_city Jones Main Harrison Smith North Rye tuples Curry North Rye y(or rows) Lindsay Park Pittsfie/d customer Haichang Gao, Software School, Xidian University 8DataBase System Haichang Gao , Software School , Xidian University 8 Mathematical Relations  The current values (relation instance, 关系实例) of a relation are specified by a table  An element t of r is a tuple(元组), represented by a row in a table  Order of tuples is irrelevant (元组是无序的 tuples may be stored in an arbitrary order) Jones Smith Curry Lindsay customer_name Main North North Park customer_street Harrison Rye Rye Pittsfield customer_city customer attributes (or columns) tuples (or rows)