第一章数据库复习.ppt

0-* The Hierarchical Data Model A corporate entity The banking branch1 The banking branch2 employee1 employee2 记录之间的联系通过指针实现，查询效率较高。但只能表示1：N的联系。 0-* The Network Data Model 记录之间的联系通过指针实现，M:N联系容易实现，查询效率较高。但编写应用程序较复杂，程序员必须熟悉数据库的逻辑结构。 学生宿舍 学生 教研室 系 教师 0-* S1 P1 300 …… S2 P1 300 S2 P2 400 -- -- --- SP P S S1 Smith 20 London S2 S3 S4 S5 P1 P2 P3 P4 P5 P6 300 200 400 200 100 100 300 400 200 200 300 400 The Network Model: Sample Values 0-* System R DB2 INGRES Oracle Informix ACCESS … SP :Shipment S# P# QTY S1 P1 300 S1 P2 200 S1 P3 400 . . . S2 P1 400 S2 P2 200 S1 Smith 20 London S2 Jones 10 Paris S3 : : : S4 : : : S: Supplier S# NAME Status City P: Parts P# P-Name Color Weight ………… P1 Nut Red 12 …… P2 Screw Blue 17 . P3 : : : : : : : : : Relational Data Model: A Sample Relational Database 0-* Person Object-Oriented Data Model Employee face-image Vehicle Company dept. salary name name location model hair-color name owns photo manu. car-video video aggregation inheritance 0-*  Customer Invoice Inventory Parts Customer No. Customer Name Customer Addr. Social Security ID Customer No. Customer Name Part No. Quantities Unit Price Part No. Part Description Unit Price Supplier Quantities Remain Quantities Ordered Part No. Part Description Supplier Quantities Ordered Customer Name Unit Price