Is 2NF a Stable Normal Form?

Traditionally, it was accepted that a relational database can be normalized step-by-step, from a set of un-normalized tables to tables in \(1NF\), then to \(2NF\), then to \(3NF\), then (possibly) to \(BCNF\). The rule applied to a table in \(1NF\) in order to transform it to a set of tables in \(2NF\) seems to be too straightforward to pose any difficulty. However, we show that, depending on the set of functional dependencies, it is impossible to reach \(2NF\) and stop there; one must, in these cases, perform the normalization from \(1NF\) to \(3NF\) as an indecomposable move. The minimal setup to exhibit the phenomena requires a single composite key, and two partially overlapping chains of transitive dependencies.