Second Normal Form
Firstly let’s have a look at Codd’s rule for Second Normal Form:
A table that is in first normal form must meet additional criteria if it is to qualify for second normal form. Specifically: a first normal from table is in second normal form if and only if, given any candidate key and any attribute that is not a constituent of a candidate key, the non-key attribute depends upon the whole of the candidate key rather than just a part of it.
Got that? No, nor have I.
Every non primary Key column must relate ONLY to the Primary Key