Types of Schema in DBMS and their Characteristics

Types of Schema in DBMS and their Characteristics 1. Physical Schema Description: This schema describes how the data is physically stored in the database. It deals with the storage and access methods, file organization, indexing, and data compression. Characteristics: Defines the storage structure and access methods. Deals with physical data storage, including tablespaces, indexes, partitions, etc. Managed by the DBA (Database Administrator) and usually hidden from end-users. Focuses on optimization for performance, such as disk space usage, data retrieval speed, and backup mechanisms. 2. Logical Schema Description: This schema defines the logical structure of the database. It represents the overall design and structure of the database, including tables, views, constraints, and relationships. Characteristics: Represents the logical view of the entire database. Defines tables, columns, data types, relationships, primary and foreign keys. Independent of the physical storage considerations. Used by developers to understand the structure and constraints of the database. Focuses on data organization, integrity, and rules governing the data. 3. View Schema (External Schema) Description: This schema defines the way end-users view the data. It consists of one or more views, which are customized presentations of the data in the database, tailored to the needs of different users. Characteristics: Represents the user’s view of the database, which can be a subset or a specific arrangement of the data. Multiple external schemas can exist for different user roles, like administrators, analysts, or general users. Provides security by restricting access to specific data. Can include specific query results, filters, or customized data presentations, such as reports. Independent of the logical and physical schemas, allowing flexibility in how data is presented without altering the underlying structure. Summary of Relationship Between Schemas: Physical Schema: How data is physically stored.
 Logical Schema:
 The structure of the entire database and its components. View Schema:
 How data is viewed by different users.

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