Instance and Schema in DBMS

What is Schema

➺ The overall logical representation of a database is called schema.
➺ The description of the database and shows how the data is stored in the database.
➺ It is a logical structure of the database.
➺ Database schema does not change frequently.
➺ RDBMS - table, student, faculty ( emp_id, emp_name, emp_past, salary).

There are 3 types of schema

1. Physical schema

➺ It represents database design at the physical level.

2. Logical schema

➺ It represents database design at the Logical level.

3. View schema

➺ It represents database design at the view or external level.

What is Instance

➺ Instance refers to the collection of data and information at a particular time.
➺ The Search queries operations do not make a change in the data of the instance
➺ It can be changed by CRUD operations such as deletion and addition of data and information.
➺ It is a Snapshot of the Database at a Specific time.
➺ Database instance changes according to the time.

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