What’s db normalization?

 

http://en.wikipedia.org/wiki/Database_normalization

Database normalization is the process of organizing the fields and tables of a relational database to minimize redundancy and dependency. Normalization usually involves dividing large tables into smaller (and less redundant) tables and defining relationships between them. The objective is to isolate data so that additions, deletions, and modifications of a field can be made in just one table and then propagated through the rest of the database via the defined relationships.

1NF
First normal form
Two versions: E.F. Codd (1970), C.J. Date (2003)
1970 ^[1] and 2003 ^[9]
Table faithfully represents a relation, primarily meaning it has at least one candidate key

2NF
Second normal form
E.F. Codd
1971 ^[2]
No non-prime attribute in the table is functionally dependent on a proper subset of any candidate key

3NF
Third normal form
Two versions: E.F. Codd (1971), C. Zaniolo (1982)
1971 ^[2] and 1982 ^[10]
Every non-prime attribute is non-transitively dependent on every candidate key in the table. The attributes that do not contribute to the description of the primary key are removed from the table. In other words, no transitive dependency is allowed.