RDBMS

An RDBMS, or relational database management system, is a database management system that stores data in structured tables based on the relational model. Data are organized into rows (records) and columns (attributes), with relationships between tables established via keys. RDBMSs provide a formal data language, typically SQL, for defining, querying, updating, and administering data.

Key concepts include relations, primary keys, foreign keys, normalization to reduce redundancy, and integrity constraints such as NOT NULL, UNIQUE, and CHECK. Foreign keys enforce referential integrity between tables. Indexes improve query performance.

An RDBMS includes components such as a storage engine, a query processor, a transaction manager, and a metadata catalog. Transactions follow ACID properties (Atomicity, Consistency, Isolation, Durability) to ensure reliable processing. Concurrency control and locking govern simultaneous access.

Common features include SQL as the standard interface, support for multiple concurrent users, transactions, views, stored procedures, and triggers. RDBMS often support data normalization, relational algebra, and optimization of queries via an optimizer.

Typical use cases include financial systems, inventory control, customer records, and any application requiring structured data and strong consistency. Popular RDBMS products include MySQL, PostgreSQL, Oracle Database, Microsoft SQL Server, IBM Db2, and SQLite; some are open-source or bundled with commercial licenses.

Limitations include challenges scaling horizontally and handling unstructured data; modern RDBMSs address this with sharding, partitioning, or distributed architectures, and with polyglot persistence alongside NoSQL systems.