Fifth Normal Form (5NF)

Concepts: dmFifthNormalForm

5NF: Decompose Complex Join Dependencies 5NF is the most theoretical normal form you are likely to encounter. A table is in 5NF when it cannot be decomposed into smaller tables without losing information when you join them back together. In practice, 5NF violations are extremely rare. The classic example: suppliers, parts, and projects. A supplier can supply a part. A supplier can work on a project. A part can be used in a project. But the three-way relationship (this supplier provides this part to this project) cannot be reconstructed from three pairwise tables. You need the ternary junction table. If the ternary relationship CAN be reconstructed from pairwise tables, it is a 5NF violation (the ternary table has a join dependency that could be decomposed). If it cannot, the ternary table