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 and only 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 and only if it is in 1NF and every non-prime attribute of the table is either dependent on the whole of a candidate key, or on another non prime attribute.
Note that when a 1NF table has no composite candidate keys (candidate keys consisting of more than one attribute), the table is automatically in 2NF.
Read more about Second Normal Form: Example
Famous quotes containing the words normal and/or form:
“In order to move others deeply we must deliberately allow ourselves to be carried away beyond the bounds of our normal sensibility.”
—Joseph Conrad (1857–1924)
“To do the opposite of something is also a form of imitation, namely an imitation of its opposite.”
—G.C. (Georg Christoph)