The database schema is a structure of the database or it is a blueprint of the database which represents the logical configuration of all or part of a relational database. It is very difficult to change the database schema after it completed.
The database schema does not contain any data or information on it.
Types of the Database schema
There are two main types of database schema:-
1.Logical database schema:- Logical database schema that defines the logical constraints that are used in stored data. It defines tables, views, constraints, integrity.
2.Physical database schema:-Physical database schema defines how the data is stored in the storage in the form of files, indices, etc.
What is the Database Instance?
The database schema and database instance is the two different terms that define different things in it, The database schema is the skeleton or the blueprint of the database. It was made when the database doesn’t exist.
Whereas The Database instance is the snapshot of the database, the database instance can be changed from time to time. Database schemas and database instances can affect one another through a database management system (DBMS).
The DBMS makes sure that every database instance complies with the constraints imposed by the database designers in the database schema.