NORMALIZATION and NORMAL FORM'S

Some Oracle databases were modeled according to the rules of normalization that were intended to eliminate redundancy.

Obviously, the rules of normalization are required to understand your relationships and functional dependencies

First Normal Form:

A row is in first normal form (1NF) if all underlying domains contain atomic values only.

• Eliminate duplicative columns from the same table.
• Create separate tables for each group of related data and identify each row with a unique column or set of columns (the primary key).

Second Normal Form:

An entity is in Second Normal Form (2NF) when it meets the requirement of being in First Normal Form (1NF) and additionally:

• Does not have a composite primary key. Meaning that the primary key can not be subdivided into separate logical entities.
• All the non-key columns are functionally dependent on the entire primary key.
• A row is in second normal form if, and only if, it is in first normal form and every non-key attribute is fully dependent on the key.
• 2NF eliminates functional dependencies on a partial key by putting the fields in a separate table from those that are dependent on the whole key. An example is resolving many: many relationships using an intersecting entity.

Third Normal Form:

An entity is in Third Normal Form (3NF) when it meets the requirement of being in Second Normal Form (2NF) and additionally:

• Functional dependencies on non-key fields are eliminated by putting them in a separate table. At this level, all non-key fields are dependent on the primary key.
• A row is in third normal form if and only if it is in second normal form and if attributes that do not contribute to a description of the primary key are move into a separate table. An example is creating look-up tables.

Boyce-Codd Normal Form:

Boyce Codd Normal Form (BCNF) is a further refinement of 3NF. In his later writings Codd refers to BCNF as 3NF. A row is in Boyce Codd normal form if, and only if, every determinant is a candidate key. Most entities in 3NF are already in BCNF.

Fourth Normal Form:

An entity is in Fourth Normal Form (4NF) when it meets the requirement of being in Third Normal Form (3NF) and additionally:

Has no multiple sets of multi-valued dependencies. In other words, 4NF states that no entity can have more than a single one-to-many relationship.