Limitations of File-based System

• Separation and isolation of data
• Duplication of data
• Data dependence

• Incompatible file formats
• Fixed queries/proliferation of application programs

Database Approach

• The description of the data is known as the system catalog (or data dictionary or metadata – the ‘data about data’). It is the self-describing nature of a database that provides program–data independence.

• Organize

  1. An entity is a distinct object (a person, place, thing, concept, or event) in the organization that is to be represented in the database.
  2. An attribute is a property that describes some aspect of the object that we wish to record.
  3. A relation-ship is an association between entities.

DBMS

Software.

Facilities

• Data Definition Language (DDL), to define the database, to specify the data types and structures and the constraints.

• Data Manipulation Language (DML), to insert, update, delete, and retrieve data. Structured Query Language (SQL), formal and standard.

• Controlled Access

• Views View mechanism.

  1. Provide a level of security.
  2. Provide a mechanism to customize the appearance of the database.
  3. Present a consistent, unchanging picture of the structure of the database.

Little Points

• The structure of the database is called the schema.
• The constraints are sometimes called business rules.