副标题副标题副标题副
(1)
(2)E-R图转化为关系模型为:
产品(GN0,GNA,GUP)
零件(PN0,PNA,UW,UP,MN0,PQTY)
材料(MN0,MNA,CU,MUP)
装配(PN0,GN0,GQTY)(4PⅢ)