Computer Basics

DBMS

Database is the organized collection and storage of data that can be easily accessed.

Database Management System (DBMS) is a software that is used to manage database. It is the interface between the user and the database and gives virtual view of data e.g. Oracle, MySQL etc.

Feature of DBMS:
• Data is structured making the data retrieval and sharing easy
• The data duplication and redundancy are reduced
• Due to organised storage of data and data integration, space is saved and cost is reduced
• Allows multiple users to access data at the same time (concurrency)
• Data integrity is maintained
• Large databases can be maintained without data loss as backup and recovery of data is possible. Thus there is durability of data
• Data is secure and only authorised users can access data
• Query language like SQL can be used to access data

Types of DBMS:
• Hierarchical DBMS
 Stores data in parent-child relationship node
 Parent can have one or more child, but child can have only one parent
• Network DBMS
 It has hierarchical structure
 Parent can have one or more child and child can have one or more parent
• Relational DBMS
 It is a database management system that allows to manipulate data in a relational database where data is stored in tables
• Object oriented DBMS
 It is a database management system where entities are represented as objects

Database architecture:
• One-tier architecture
 The client, server and database are all present on same machine
 User can directly access database
• Two-tier architecture
 The application is at client side and the database is at the server side
 The client and server communicate with APIs like JDBC, ODBC etc.
• Three-tier architecture
 The client communicates with the application server and the application server communicates with the database
 Used in large applications

Types of Databases:
• Centralized database
 Located in centralized location
 Users can access the database remotely
• Distributed database
 Data is distributed among various systems
 The various systems are linked
• Relational database
 It defines relationships between tables which are rows and columns of data
 Example are Oracle, SQL Server etc.
• Object-Oriented database
 The data is stored as objects
 It has attributes and methods
• Cloud database
 Data is stored in virtually
 The user can access the database on the network
• NoSQL database
 It stores wide range of datasets
 It stores data in various ways including tabular form
• OLTP database
 Used for fast processing of data
 Used in cases where database is accessed by multiple users at same time
• Personal database
 The data is stored in personal computers
 It is accessed by small group of people

• Hierarchical database
 It has parent-child relationship
 Each parent can have one or more child but child can have only one parent
• Network database
 It has hierarchical structure
 Each parent can have one or more child and each child can have one or more parents
• Operational database
 Real-time database
 Used for daily data operations
• Enterprise database
 All the authorised users of the enterprise has access to this database
 It has large amount of data