WHAT IS A DATABASE ? a collection of data organized to help easy retrieval & usage

DATABASE CENTRALISES THE DATA MINIMISES REDUNDANCY

WHAT IS DATABASE MANAGEMENT SYSTEM ? A tool to manage and interact with the database. MANAGES DATA EFFICIENTLY

Features of DBMS Acronym for database management system permits centralisation of data enables data storage Manages data efficiently Helps in creation and maintenance of data structures Provides access to the stored data by application programs

Allows concurrent access to many users Helps to serve many applications Applicatios need not contain the database structure Enforces securilty and privacy

Enables data entry and data loading Through indexing, data manipulation is faster Provides consistency among different rows Protects data through backup/ recovery Data / program independence

ELIMINATION OF DATA DUPLICATION / REDUNDANCY DATA TO BE SHARED BY DIFFERENT APPLICATIONS ARE POOLED IN DATABASE. THIS AVOIDES DATA REDUNDANCY

DATA INTEGRITY THROUGH VALIDATION PROCEDURES BEFORE / AFTER DATA STORAGE DATA SECURITY ACCESS OF DATA IS ONLY THROUGH PROPER CHANNELS & AUTHORISATION CHECKS. THIS PROTECTS THE DATA.

DATABASE MODELS HIERARCHICAL MODEL NETWORK MODEL RELATIONAL MODEL

HIERARCHICAL MODEL FIRST USED BY IBM IN 1968 IN INFORMATION MANAGEMENT SYSTEM (IMS). IT HAS A TREE STRUCTURE WITH NODES AND BRANCHES

Hierarchical model Stores data in a tree-like structure. Assumes a parent-child relationship between the data. The top of the tree, known as the root, can have any number of dependents. Dependents, in turn, can have any number of sub-dependents, and so on. Hierarchical database systems are now obsolete.

NETWORK MODEL AN IMPROVEMENT OVER HIERARCHICAL MODEL. PARENT - CHILD RELATIONSHIPS ARE USED. HELPS RAPID AND EASY ACCESS TO DATA THROUGH MULTIPLE ACCESS PATHS TO DATA ELEMENTS SUPPORTS ONE-TO-ONE, ONE-TO- MANY AND MANY-TO-MANY RELATIONS

NETWORK MODEL Stores data in the form of records and links. Allows more flexible many-to-many relationship than do hierarchical DBMSs. Enables fast access and efficient storage Allowed complex data structures but were highly inflexible required tedious design. Example: airline reservation system

RELATIONAL MODEL TREATS DATA THROUGH THE CONCEPT OF RELATIONSHIPS RELATES DATA USED IN ONE TABLE TO DATA IN ANOTHER TABLE THROUGH A COMMON DATA ELEMENT.

RELATIONAL MODEL Has the simplest structure, a database can have. Here, data is organized in tables Tables, in turn, consist of records Records have fields. Each field corresponds to one data item. Two or more tables can be linked (joined) through common fields

RELATIONAL MODEL Easy to use Has flourished in the last decade. Commonly used on low-end computer systems. In the last few years Of late, it’s use has expanded to more powerful computer systems Popular RDBMSs are Oracle, Sybase, Ingress, SQL Server, DB2(IBM) and Informics

RDBMS DATA IS ORGANISED IN TWO-DIMENSIONAL TABLES DATA INTEGRITY IS ENSURED USING INTEGRITY CONSTRINTS DATA CONSISTENCY DATA SECURITY DATA CONCURRENCY