What is "second normal form"

n. (context databases English) A stage in the normalization of a relational database in which it is in first normal form and every non-key attribute is dependent upon the entire primary key.

Second normal form (2NF) is a normal form used in database normalization. 2NF was originally defined by E.F. Codd in 1971.

A table that is in first normal form (1NF) must meet additional criteria if it is to qualify for second normal form. Specifically: a table is in 2NF if it is in 1NF and no non-prime attribute is dependent on any proper subset of any candidate key of the table. A non-prime attribute of a table is an attribute that is not a part of any candidate key of the table.

Put simply, a table is in 2NF if it is in 1NF and every non-prime attribute of the table is dependent on the whole of every candidate key.