Relationals

Relationals are a fundamental concept in database theory and practice. They are based on the mathematical theory of relations, as formalized by E.F. Codd. A relational database organizes data into one or more tables, also known as relations. Each table consists of rows, representing individual records or tuples, and columns, representing attributes or fields.

The structure of a relational table is defined by its schema, which specifies the names and data types of each column. Data integrity is maintained through constraints such as primary keys, which uniquely identify each row within a table, and foreign keys, which establish relationships between tables by referencing primary keys in other tables.

Data within a relational database is accessed and manipulated using a relational algebra or a query language like SQL (Structured Query Language). These languages provide a set of operations to select, project, join, and combine data from various tables. The relational model's emphasis on data independence, integrity, and a standardized query language has made it the dominant model for structured data storage and management for decades. Its success lies in its ability to represent complex data relationships in a clear and logical manner, making it suitable for a wide range of applications.