Understanding normalization concept

Database normalization is the process of structuring a relational database in accordance with a series of so-called normal forms in order to reduce data redundancy and improve data integrity.

Normalization entails organizing the columns (attributes) and tables (relations) of a database to ensure that their dependencies are properly enforced by database integrity constraints.

Side effects

Side-effects may arise in relations that have not been sufficiently normalized:

• Update anomaly (change may need to be applied to multiple records; if update partially successful – data inconsistency appears)

• Insertion anomaly (all attributes should be filled during insertion; if not – data integrity compromised)

• Deletion anomaly (deletion of data representing certain facts necessitates deletion of data representing completely different facts)

Normalization Forms

UNF - Unnormalized form

1NF - First normal form

• Each sell to be Single valued

• Entries in a column are same type

• Rows uniquely identified (add Unique ID or add more columns to make unique)

2NF - Second normal form

• 1st normal form

• All attributes (Non-Key Columns) dependent on the key

3NF - Third normal form

• 2nd normal form

• All fields (columns) can be determined Only by the Key in the table and no other column

4NF - Fourth normal form

• 3rd normal form

• No multi-valued dependencies