Relational Model

The relational model, proposed by E.F. Codd in 1970, is the most dominant data model used for database management today. Its simple and elegant structure is the foundation for nearly all modern database systems, including MySQL, PostgreSQL, and SQL Server. The fundamental concept in the relational model is the 'relation,' which is a table with rows and columns. Each row in the table, formally called a 'tuple,' represents a single record or data item. Each column, formally called an 'attribute,' represents a property of that record. Every attribute has a 'domain,' which is the set of all possible values for that attribute (e.g., the domain for a 'gender' attribute might be {'Male', 'Female', 'Other'}). A key characteristic of the relational model is that the order of rows and columns is not important. Data is retrieved based on its values, not its position. Relationships between tables are established through the use of keys. A primary key is a column (or set of columns) that uniquely identifies each row in a table. A foreign key is a column in one table that references the primary key of another table, thereby creating a link between them. The model's strength lies in its simplicity, flexibility, and the strong mathematical foundation of set theory and relational algebra, which provides a basis for powerful and consistent query languages like SQL.