Introduction to Database System
- A database Management System is a collection of interrelated data and a set of programs to access those data.
- The primary goal of a DBMS is to provide an environment that is both convenient and efficient for people to use in retrieving and storing information.
- Database system is ubiquitous today, and most people interact, either directly or indirectly with database many times every day.
Applications of Database System:
- Shopping Malls
- Medium/Large Scale Business
Disadvantages of File Processing Systems
- Data Redundancy and inconsistency
- Difficulty in accessing data.
- Data isolation.
- Integrity problems.
- Atomicity problems.
- Concurrent Access anomalies.
- Security issues.
Data Abstraction: The system hides certain details of how the data are stored and maintained.
- Physical Level Abstraction: How the data are actually stored.
- Logical Level Abstraction: What data are stored in the database and what relationship among those data.
- View Level: Only part of the data is visible.
The collection of information stored in the database at a particular moment is called an instance of the database.
The overall design of the database is called the database schema.
- Physical Schema.
- Logical Schema.
Data Models: A collection of conceptual tools for
- Describing data,
- Data relationships,
- Data semantics and
- Consistency constrains.
Categories of Data Models:
- Relational Model
- The Entity – Relationship Model
- Object based data model
- Semi structured data model.
A Query is a statement requesting the retrieval of information.
The portion of a DML that involves
- Data Definition Language (DDL):
- Data Manipulation Language(DML):
- Retrieval of information stored in the database.
- Insertion of new information.
- Deletion of information.
- Modification of information.
Data Storage and Querying: Database system is broadly divided into storage manager and query processor.
Storage Manager: A storage manager is a program module that provides the interface between the low level data stored in the database and the application programs and queries submitted to the system.
- Storage Manager (Physically: Data Files, Data Dictionary, Indices)
- Authorization and integrity manager.
- Transaction manager
- File Manager
- Buffer Manager
- Query Processor
- DDL interpreter
- DML compiler
- Query Evaluation Engine.
- Transaction Management.
Different Types of Users:
- Naïve Users
- Application Programmers
- Sophisticated Users.
- Specialized Users.
Functions of Database Administrators:
- Schema Definition
- Storage structure and access method definition.
- Schema and physical organization modification.
- Granting of authorization for data access.
- Routine maintenance.