What is a relational database?

A relational database organizes data into tables (relations) with rows (tuples) and columns (attributes). Tables are linked to each other via keys (primary and foreign keys), establishing relationships. It is based on the relational model proposed by E.F. Codd in 1970. Data is queried using SQL (Structured Query Language). Relational databases enforce data integrity via constraints, support ACID transactions, and are excellent for structured data with well-defined schemas. Examples: MySQL, PostgreSQL, Oracle, SQL Server, SQLite.