Instance and Schema in DBMS
What is SCHEMA- Design of database is called the Schema. It is basically skeleton structure that represent the logical view of entire database. It defines how data is organised and how the relationship among them are associated. It formulates all the constraints that are to be applied on the data. Database system has various schemas.
Physical database schema:
- It describes how data will be stored in hard disc / secondary storage device.
- It describes the database design at physical level.
- The schema related to the actual storage of data and its form of storage like file, indices.
Logical database schema: this schema define all the logical constraints that need to be applied on the data storage.
- It Defines table, views, and integrity constraint.
- Define relationship between table and keys applied.
View Schema: It describes different views of database and sometime also called subschema.
Instance:Collection of information stored in the database at a particular moment is called an instance.
Table Student St_Name St_Id St_Gender What Is an Instance---> Deepak 889 male