資料庫(2)

第二章 Data Model

Data Model:A set of concepts to describe the structure of a database, and certain constraints that the database should obey.

Components of Data Model

1.Structures

2.Operations

3.Integrity Constraints

Data Model為了將資料抽象化,將storage detail隱藏

Relational Data Model

Hierarchical Data Model

Network Data Model

Primary Key:滿足uniqueness和minimality的candidate key

Foreign key:a foreign key is an attribute of relation R2 whose values are refer to the primary key of some relation R1.