士 4.1.3外来键 RELATION P(产品号,产品名,产品型号) PRIMARY KEY(产品号) RELATION GP(零件号,零件名,零件重量, 单价) PRIMARY KEY(零件号) RELATION PGP(产品号,零件号,数量) PRIMARY KEY(产品号,零件号4.1.3 外来键 RELATION P(产品号,产品名,产品型号) PRIMARY KEY(产品号) RELATION GP(零件号,零件名,零件重量, 单价) PRIMARY KEY(零件号) RELATION PGP(产品号,零件号,数量) PRIMARY KEY(产品号,零件号)