Schema and Sub schema

schema subschema


Schema and sub schema is the structure that represent hows database are used for data insertion ,updation and deletion data. The schema i the database design. The schema is designed for developer for understanding hows data can be stored in to database and hows they extract from database.

the database schema defines relationship between entities between each other. The database designer basically design the schema designing. This is generally stored into data dictionary.

The schema divide into 2 parts-

  1. Physical/Internal Schema
  2.  conceptual/Logical Schema

schema subschema

We discuss each type in detail below.

  1. Physical/Internal Schema-

In that stage defines hows data was stored in to database. The all data stored into hard disk in that include  blocks for storing data.

2. Conceptual/Logical Schema-

In that stage defines data types and data relationship between each other. In that stage also working for constraints. the DBA(Database Administrator) is totally responsible for that stage working or maintenance. That level also called as conceptual level. In that stage all query executed as per user requirement.

Sub Schema-

the sub schema is used for display schema operations to user. Sub schema shows to user a different formations of database and schema operations to users mainly. Sub schema is application software, end user or view stage. That is the end user operation , the all operations and query execution display to user in that stage. The DML and DDL commands accepted from user with use of view or end user stage.

Database Instance

The group of information stored in a database at a particular moment is called database instance.

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