【数据库系统】数据抽象的三个层次

Data abstraction

Database system provides an abstract view of the data. Hide certain complexity details of how data is stored and maintained.

Achieved through several level of abstraction

• Physical level
• Logical level
• View level

Physical level

Physical level describes how a record (e.g. customer) is stored.

Only designers can see.

Logical level

Logical level describes what data are stored in the database, an