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Describe data schema and instances.

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By Dipali Umre

Database Schema:

  1. Definition: The database schema is like the blueprint or design of a database. It outlines how the data is organized, what types of data can be stored, and the relationships between different pieces of data.
  2. Stability: Once designed, the schema doesn’t change frequently. It’s a stable framework that guides how data is stored and accessed.
  3. Representation: A schema can be visually represented using a schema diagram. This diagram usually shows the names of different data entities (like tables) and their attributes.

Example: Schema Diagram for a Student Database

Student (Name, Student_number, Class, Branch)

Course (Course_name, Course_number, Department)

Database Instances:

  1. Definition: The data in the database at a specific moment is called a database state or snapshot. This represents the current set of data in the database.
  2. Variability: Database states can change as we add, delete, or modify records. Each state reflects the current situation of the data.
  3. Multiple States: Different actions, like inserting a new record or updating an existing one, lead to different states. So, you can have many states of the database while following the same schema.
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