103 Overview of Relational Databases

A type of database that stores and organizes data in tables with rows and columns, representing entities and their relationships. These tables are connected through keys, enabling efficient querying and data management.

Edgar F.Codd, in 1970, introduced the relational model, revolutionizing database management by introducing table-based data structure and relationships. This approach replaced older models, like hierarchical and network models.

Each table in a relational database represents a single entity (e.g., customers, products). Relationships between tables are established through keys, allowing for combining data from multiple tables.

The primary components of a table in a relational database are rows and columns. Rows represent individual records or entries, and columns represent specific attributes or fields.

A key is a special column in a relational database table used to uniquely identify each row, enabling relationships with other tables. There are primary keys (unique identifier within a table) and foreign keys (references another table's primary key).

Relationships between tables in a relational database are defined using keys. These relationships, such as one-to-one, one-to-many, or many-to-many, specify how data from different tables can be linked and queried.

Structured Query Language (SQL) is the standard language for managing and manipulating data in relational databases. It allows users to perform operations like inserting, updating, deleting, and retrieving data from tables.

The relational model is a database management system that organizes data into tables with relationships, offering advantages such as data independence, flexibility, and standardized querying with SQL. This model enables efficient data management and retrieval.

Rows represent individual records, with each row containing values for each attribute.

Columns define the structure by specifying the attributes or fields of the entity, such as customer name or product price, along with their data types and constraints.

A primary key uniquely distinguishes each record within a table, preventing duplicate entries and enabling efficient data retrieval.

Relationships between tables use constraints and keys to enforce data consistency and integrity, ensuring accurate and reliable data across the database.

SQL (Structured Query Language) is a powerful tool for interacting with relational databases, enabling users to perform a wide range of operations like selecting specific data from multiple related tables through JOIN operations, filtering results with WHERE clauses, and summarizing data using aggregate functions like COUNT, SUM, and AVG.

Security in relational databases is managed through authentication and authorization processes. Administrators can define user roles and permissions, restricting access to sensitive data and operations based on user privileges. This ensures that data is protected from unauthorized access and modifications, maintaining the overall security and integrity of the database.

Data independence ensures that changes to the database schema, such as adding new columns or modifying table structures, do not require changes to the application code that interacts with the database.

MySQL is favored for its reliability and ease of use in web development environments.

PostgreSQL offers advanced features like complex queries and extensibility.

Oracle Database provides robust performance and support for large-scale enterprise applications.

Microsoft SQL Server integrates seamlessly with other Microsoft products, making it a preferred choice for businesses using the Microsoft ecosystem.

SQLite is ideal for applications that require a simple, serverless database solution due to its lightweight nature.

By using primary and foreign keys to establish relationships between tables, relational databases enforce referential integrity, preventing orphaned records and ensuring that related data remains synchronized.

While relational databases offer benefits like data consistency and flexible querying, they can introduce complexity in schema design and may not perform as well with very large-scale or unstructured data compared to NoSQL databases.

In a relational database, keys are specific columns used to uniquely identify individual records within a table. These keys form the foundation for establishing relationships between tables, enabling efficient retrieval of interconnected data.

Constraints play a crucial role in maintaining data integrity within relational databases by enforcing rules on the data and ensuring only valid data is stored.

An organization might choose PostgreSQL over MySQL for its more advanced features, such as support for complex data types, full-text search, and custom functions, making it suitable for applications that require sophisticated data handling.

SQLite is particularly well-suited for mobile applications and small-scale projects due to its lightweight and embedded nature, allowing it to operate without a separate server process.

Data independence in relational databases allows changes to the database schema without impacting the application layer, simplifying maintenance and enabling easier scalability as the data model evolves.

In an e-commerce database, tables like 'Customers,' 'Orders,' and 'Products' can be related through keys like CustomerID and ProductID, enabling queries that retrieve detailed purchase information for each customer.

Relational databases use structured tables with defined relationships, while NoSQL databases use flexible, schema-less models like document, key-value, or graph structures, making them suitable for managing diverse data formats.

Edgar F. Codd introduced the relational model, a groundbreaking approach to database management based on tables and relationships, replacing older models. This innovation revolutionized how we store and manage data.