Relationsmodellen

Relationsmodellen, commonly called the relational model, is a database model introduced by E. F. Codd in 1970. It represents data as relations, or tables, composed of tuples (rows) and attributes (columns). A database schema defines a set of relations; each relation has a primary key that uniquely identifies its tuples. Data integrity is maintained by constraints, including referential integrity via foreign keys that link relations together. The model draws on predicate logic and set theory, enabling declarative queries rather than navigational data access.

Core concepts include relations, attributes, domains, and keys. A relation’s state is a set of tuples that satisfy its integrity constraints. Queries are expressed in relational operators derived from relational algebra and relational calculus, and the practical standard for querying relational databases is Structured Query Language (SQL), which implements many of these operations.

Normalization is a key practice in the relational model. By decomposing data into smaller, well-structured relations and organizing attributes into normal forms (1NF, 2NF, 3NF, BCNF), redundancy is reduced and update anomalies are minimized. This supports data independence, allowing changes in storage or access methods without altering the logical data design.

Impact and usage: the relational model underpins most traditional database systems and remains dominant for structured data. It provides a clear, mathematically grounded framework for data organization, integrity, and query processing, while evolving with extensions and performance optimizations in modern RDBMS.