second normal form

the test for 2NF involves testing for functional dependencies whose left-hand side attributes are part of the primary key. if the primary key contains a single attribute, the test need not be applied at all. if a relation schema is not in 2nf, it can be second normalized or 2nf normalized into a number of 2NF relations in which nonprime attributes are associated only with the part of the primary key on which they are fully functionally dependent.
[cite:;see @elmasri_db_2015 chapter 14 basics of functional dependencies and normalization for relational databases]

a relation pertains the 2nf normalization degree if

• it pertains the 1nf normalization degree;
• every field that isnt part of a key is fully functionally dependent on the whole key. i.e. a field that isnt part of the key cannot be functionally dependent on only part of the key.

in a relation with 1 field only the 2nf normalization degree is vacuously satisfied.
the process of 2nf normalization is as follows. when a partial functional dependency is present, denoted by where is part of the key:

1. we copy the functional dependency into a new relation, in which is the key.
2. we delete from the original relation.