Normal Forms (Part 1) Steven Le ~ CS157B

Normalization is a systematic way of ensuring that a database structure is suitable for general-purpose querying and free of certain undesirable characteristics—insertion, update, and deletion anomalies—that could lead to a loss of data integrity.

In English: Normalization is a well-defined way to structure a database so that weird things don’t happen to your data when you use it

Normal Forms Edgar Codd, the inventor of the relational model, also introduced the concept of Normalization and Normal Forms (NF) Normal Forms are criteria for determining a table's degree of vulnerability to logical inconsistencies and anomalies

Edgar Codd Created First Normal Form (1NF) in 1970 Created Second Normal Form (2NF) and Third Normal Form (3NF) in 1971 With Raymond Boyce, created Boyce-Codd Normal Form (BCNF) in 1974

There also exists other Normal Forms invented by other people. These include 4NF, 5NF, and 6NF We will be looking at 1NF, 2NF, and 3NF

Normal Form Properties The higher the Normal Form a table has, the less vulnerable to inconsistencies and anomalies it is A table always meets the requirements of its Highest Normal Form (HNF), as well as all the requirements of all lower Normal Forms A table does not meet the requirements of Normal Forms higher than its HNF

Achieving a Normal Form is NOT step-wise i.e. 1NF -> 2NF -> 3NF Rather, you design the table to be around 3NF on the first try. This is usually the minimum for a table to be considered “Normalized”. Once there, it should be easier to achieve higher Normal Forms

Vocab Overview Superkey Candidate Key Primary Key Prime Attribute Dependency

Superkey a set of attributes of a relation variable for which it holds that in all relations assigned to that variable there are no two distinct tuples (rows) that have the same values for the attributes in this set

Candidate/Primary Key Candidate Key: Superkey with no proper subsets that are also superkeys Primary Key: Candidate Key with no NULL values Prime Attribute: Attribute part of the Candidate Key

Dependency X → A: The attribute set “X” determines set “A” Trivial Functional Dependency: X → Y is called trivial if Y is a subset of X

First Normal Form A table is said to be in First Normal Form if it faithfully represents a relation No repeating groups last NameFirst NameNickname CoddEdwardE-Money DavisBaronBoom Dizzle DavisBaronBD

Second Normal Form A table is 2NF 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

Person (Not 2NF)PetVeterinarian JohnCatDr. Howard JohnDogDr. Howard PaulBirdDr. Dre AndyCatDr. Dre Person (2NF)Pet JohnCat JohnDog PaulBird AndyCat Person (2NF)Veterinarian JohnDr. Howard PaulDr. Dre AndyDr. Dre

Third Normal Form A table is in 3NF if for each of its functional dependencies X → A, at least one of the following conditions holds: X contains A (that is, X → A is trivial functional dependency), or X is a superkey, or A is a prime attribute (i.e., A is contained within a candidate key)

Tournament (2NF)YearWinnerWinner DOB Peruvian Open1989Tom10/28/75 Westgate Masters1993Kurt6/9/69 Bolivian Open1986Tom10/28/75 Peruvian Open1993Blaire5/7/90 Tournament (3NF)YearWinner Peruvian Open1989Tom Westgate Masters1993Kurt Bolivian Open1986Tom Peruvian Open1993Blaire Player (3NF)Winner DOB Tom10/28/75 Kurt6/9/69 Blaire5/7/90

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