Relational Databases Overview PDF

103 Overview of Relational Databases A relational database is a type of database that stores and organizes data in tables, which ** **...

103 Overview of Relational Databases A relational database is a type of database that stores and organizes data in tables, which ** ** * * are made up of rows and columns. * * * * * Each table in a relational database represents an entity (e.g., customers, products) and is * *** *** * * * * related to other tables through defined relationships. * * The relational model was introduced by Edgar F. Codd in 1970 and revolutionized how data * * is managed and structured in databases. ** Example: An e-commerce database may have separate tables for customers, orders, ** *** *** * * and products. These tables are related through keys that allow a query to combine data (e.g., finding *** *** * * the products each customer purchased). Core Concepts of Relational Databases ** Tables (Relations): ** The primary structure in a relational database, where data is stored in rows and * * * * * columns. * * Each table has a unique name and contains data about a single type of entity. * * * ** Rows (Tuples): * * ** * Each row represents a single record in the table. * *** *** *** *** A row contains all the attribute values for a particular instance of the entity. *** ** * ** Columns (Attributes): * * ** Columns represent the fields or properties of the entity (e.g., customer name, *** *** product price). Each column has a specific data type and constraint. * * * * *** Primary Key: * ** A unique identifier for each row in a table. *** *** It ensures that no duplicate records exist in the table. ~~ ~~ ** Example: A CustomerID column that uniquely identifies each customer. ** ` ` * * * ** ** * Benefits of Relational Databases ** Data Consistency and Integrity: Relationships between tables ensure consistent and * * * *** *** *** * * * accurate data through constraints and keys. ** ** ** ** * *** Flexibility in Queries: SQL allows complex queries that can join multiple tables, filter * ** * * *** ** * *** ** data, and aggregate information. * *** ** * ** Security and Permissions: Robust user access control mechanisms ensure that only ** * authorized users can view or modify data. * ** == Data Independence : Applications are separated from the physical data structure, * *== ** *** ** ** *** * which simplifies modifications without affecting the applications using the data. ** ** ** ** * Common Relational Database Management Systems * * (RDBMS) ** MySQL: Open-source, widely used for web applications. ** *** *** *** *** ** PostgreSQL: Advanced, open-source RDBMS with extensive features. ** *** *** *** *** *** *** ** Oracle Database: Known for its scalability and enterprise-level support. ** *** *** *** *** ** Microsoft SQL Server: A popular choice for businesses running Microsoft-based ** *** applications. *** ** SQLite: A lightweight, embedded relational database often used for mobile ** *** *** *** *** applications and small-scale projects. We will learn more about relational databases in the upcoming chapters.