DataBase System K Mathematical Relations H Al, A2,..., An are attributes R=(A1,A2,…,An) is a relation schem(关系模式) E.g. Customer-schema customer-name, customer-street, customer-city H r(R)is a relation on the relation schema r E. g. customer( Customer-schema) Haichang Gao, Software School, Xidian UniversityDataBase System Haichang Gao , Software School , Xidian University 7 Mathematical Relations  A1 , A2 , …, An are attributes  R = (A1 , A2 , …, An ) is a relation schema(关系模式) E.g. Customer-schema = (customer-name, customer-street, customer-city)  r(R) is a relation on the relation schema R E.g. customer (Customer-schema)