Normalisierungsstufe

Normalisierungsstufe, also known as normalization level, refers to the degree to which a relational database schema satisfies certain formal requirements designed to reduce redundancy and prevent undesirable characteristics such as update anomalies. The concept originated in the early 1970s with Edgar F. Codd, who introduced a series of normal forms. At most five normal forms are commonly discussed: first normal form (1NF), second normal form (2NF), third normal form (3NF), Boyce‑Codd normal form (BCNF), and fourth normal form (4NF). Fifth normal form (5NF), also called projection‑decomposition normal form (PDNF), addresses join dependencies, and the eighth normal form (8NF) handles temporal data.

Each successive normal form imposes stricter constraints. For instance, 1NF requires atomic column values; 2NF eliminates partial dependencies on a composite key; 3NF removes transitive dependencies; BCNF resolves remaining functional dependency anomalies. A database schema is said to be at a particular normal form if it satisfies the axioms of that form but not necessarily the next. Tools such as entity‑relationship models, functional dependency analysis, and normalization algorithms are employed to determine and enforce a given normalisierungsstufe.

Normalization is not an absolute end; practical considerations often dictate a balance between normalization and performance. Highly normalized schemas can lead to excessive joins, while denormalization may simplify queries at the cost of redundancy. Normalisierungsstufe therefore serves as a guideline rather than an absolute rule, enabling database designers to assess trade‑offs in the structure of relational data.