An RDBMS, or Relational Database Management System, is a type of database management system (DBMS) that stores data in a structured format using tables, which are organized into rows and columns. RDBMSs use Structured Query Language (SQL) for querying and managing data. The relational model, introduced by Dr. Edgar F. Codd in 1970, is based on the concept of relations (tables) and ensures that data is stored in a way that maintains relationships between different data sets.
Key characteristics of an RDBMS include:
Tables: Data is organized into tables (also known as relations), where each table consists of rows (records) and columns (fields). Each column represents an attribute of the data, and each row represents a unique record.
Schema: An RDBMS uses a schema to define the structure of the database, including the tables, columns, data types, constraints, and relationships between tables. The schema serves as a blueprint for how data is organized and maintained.
Primary Keys: Each table has a primary key, which is a unique identifier for each record. The primary key ensures that each row in the table is distinct and can be referenced by other tables.
Foreign Keys: Foreign keys establish relationships between tables by linking columns in one table to the primary key of another table. This enforces referential integrity, ensuring that relationships between tables remain consistent.
Normalization: Normalization is the process of organizing data to reduce redundancy and improve data integrity. It involves dividing large tables into smaller, related tables and defining relationships between them.
SQL (Structured Query Language): SQL is the standard language used to interact with an RDBMS. It provides commands for querying, inserting, updating, and deleting data, as well as defining and managing the database schema.
Transactions: An RDBMS supports transactions, which are sequences of operations performed as a single unit. Transactions ensure that a series of operations either complete successfully or leave the database in a consistent state. Transactions follow the ACID properties (Atomicity, Consistency, Isolation, Durability) to maintain data integrity.
Data Integrity and Constraints: RDBMSs enforce data integrity through constraints, such as uniqueness, referential integrity, and domain constraints. These constraints ensure that data adheres to specified rules and remains accurate and consistent.
Concurrency Control: RDBMSs manage concurrent access to data by multiple users or processes, ensuring that transactions are executed in a way that prevents conflicts and maintains data consistency.
Backup and Recovery: RDBMSs provide mechanisms for backing up and recovering data to protect against data loss and ensure data availability in case of failures.
Examples of popular RDBMSs include MySQL, PostgreSQL, Oracle Database, Microsoft SQL Server, and SQLite. These systems are widely used in various applications, from small-scale projects to large enterprise systems, due to their robustness, scalability, and ability to manage structured data efficiently.
