1st Normal Form (1NF)
A table (relation) is in 1NF if:
1. There are no duplicated rows in the table.
2. Each cell is single-valued (no repeating groups or arrays).
3. Entries in a column (field) are of the same kind.
*The requirement that there be no duplicated rows in the table means that the table has a key (although the key might be made up of more than one column, even possibly, of all the colomns).
2nd Normal Form (2NF)
A table is in 2NF if it is in 1NF and if all non-key attributes are dependent on all of the key. Since a partial dependency occurs when a non-key attribute is dependent on only a part of the composite key, the definition of 2NF is sometimes phrased as, “A table is in 2NF if it is in 1NF and if it has no partial dependencies.”
3rd Normal Form (3NF)
A table is in 3NF if it is in 2NF and if it has no transitive dependencies.
Boyce-Codd Normal Form (BCNF)
A table is in BCNF if it is in 3NF and if every determinant is a candidate key.
4th Normal Form (4NF)
A table is in 4NF if it is in BCNF and if it has no multi-valued dependencies.
5th Normal Form (5NF)
A table is in 5NF, also called “Projection-join Normal Form” (PJNF), if it is in 4NF and if every join dependency in the table is a consequence of the candidate keys of the table.
Domain-Key Normal Form (DKNF)
A table is in DKNF if every constraint on the table is a logical consequence of the definition of keys and domains.