Relational databases are a type of database management system (DBMS) that organizes data into tables, which are composed of rows and columns. These databases are based on the relational model, proposed by Edgar F. Codd in 1970, and they have been widely adopted in various industries.
Here are some key concepts and features of relational databases:
Tables: Relational databases store data in tables, which consist of rows (also called records or tuples) and columns (also called attributes). Each row represents a single entity, and each column represents a specific piece of information about that entity.
Primary Key: A primary key is a unique identifier for each row in a table. It ensures that each record can be uniquely identified and helps enforce data integrity.
Relationships: Relationships between tables are established using keys. The most common type of relationship is the foreign key, which is a column in one table that refers to the primary key of another table. It enables data to be linked across multiple tables, forming meaningful connections.
Data Integrity: Relational databases enforce data integrity rules to maintain the consistency and accuracy of data. These rules include primary key constraints, foreign key constraints, unique constraints, and check constraints.
ACID Transactions: Relational databases typically support ACID (Atomicity, Consistency, Isolation, Durability) transactions. ACID transactions ensure that database operations are executed reliably and consistently, even in the presence of failures or concurrent access.
Structured Query Language (SQL): Relational databases use SQL as the standard language for defining, manipulating, and querying data. SQL provides a comprehensive set of commands for creating tables, inserting, updating, and deleting data, as well as performing complex queries and aggregations.
Scalability and Performance: Relational databases can handle large volumes of data and are designed to provide efficient storage and retrieval mechanisms. They offer various indexing techniques, query optimization, and caching mechanisms to enhance performance.
Normalization: Relational databases employ normalization techniques to eliminate data redundancy and maintain data integrity. Normalization involves organizing data into multiple tables to reduce data duplication and improve data consistency.
Popular Relational Database Management Systems (RDBMS): There are several popular RDBMS implementations, including MySQL, PostgreSQL, Oracle Database, Microsoft SQL Server, and SQLite. Each RDBMS may have specific features, performance characteristics, and administration tools.
While relational databases have been the dominant choice for data storage and management, other database models, such as NoSQL databases and NewSQL databases, have emerged to address specific use cases and scalability requirements. Nonetheless, relational databases remain a fundamental and widely used technology in the field of data management.