View of Database

View of Database

It refers that how the database is actually stored in database, what data and structure of data used by the database for data. Abstraction is one of the main features of database systems. Hiding irrelevant details from the user and providing an abstract view of data to users helps in easy and efficient user-database interaction. In the previous tutorial, we discussed the three-level of DBMS architecture, The top level of that architecture is “view level”. The view level provides the “view of data” to the users and hides the irrelevant details such as data relationship, database schema, constraints, security etc from the user. To describe all this database provides the user with views and these are

• · Data abstraction
• · Instances and schemas

Data Abstraction

Database systems are made-up of complex data structures. To ease the user interaction with database, the developers hide internal irrelevant details from users. This process of hiding irrelevant details from the user are called data abstraction.

Instances and schemas

Definition of schema: The design of a database is called the schema. Schema is of three types: Physical schema, logical schema, and view schema. The design of a database at a physical level is called physical schema, how the data stored in blocks of storage is described at this level. Design of database at a logical level is called logical schema, programmers and database administrators work at this level, at this level data can be described as certain types of data records gets stored in data structures, however, the internal details such as the implementation of data structure are hidden at this level (available at the physical level). The design of database at view level is called view schema. This generally describes end-user interaction with database systems.

Definition of instance: The data stored in the database at a particular moment of time is called an instance of the database. Database schema defines the variable declarations in tables that belong to a particular database; the value of these variables at a moment of time is called the instance of that database.