Self-Doubt

Question

We say every bcnf is 3nf also but suppose in a bcnf relation the dependency is not preserved then how can we say that it is in 3nf since every 3nf must be dependency preserving.

Comments

every 3NF decomposition is not Dependency Preserving.

But there exist a 3NF decomposition for the given table which is loss-less and Dependency preservation.

check this https://gateoverflow.in/223761/normalization-3nf-doubt

Answer 1

Let's take if you have to convert a relation in 2NF, What we check after conversion.

1. there should be loss-less decomposition.

2. FD should be preserved.

Note: We check this all the normal form before going to BCNF.

So, if the relation is not in BCNF. then it will be in 3NF and FD will be preserved.