Database Normalization Forms to Know for Intro to Database Systems

Database normalization is key to organizing data efficiently. It involves structuring tables to reduce redundancy and improve integrity. Understanding the different normalization forms helps create a solid foundation for building reliable and effective database systems.

1. First Normal Form (1NF)

   • Ensures that all columns in a table contain atomic (indivisible) values.
   • Each entry in a column must be of the same data type, and each column must have a unique name.
   • No repeating groups or arrays are allowed; each record must be unique.
   • The table must have a primary key to uniquely identify each row.

2. Second Normal Form (2NF)

   • Builds on 1NF by ensuring that all non-key attributes are fully functionally dependent on the primary key.
   • Eliminates partial dependencies, where non-key attributes depend only on part of a composite primary key.
   • Requires that each non-key attribute is related to the entire primary key, not just a portion of it.
   • Helps reduce data redundancy and improve data integrity.

3. Third Normal Form (3NF)

   • Further refines 2NF by removing transitive dependencies, where non-key attributes depend on other non-key attributes.
   • Ensures that all attributes are only dependent on the primary key.
   • Promotes a more streamlined database structure, reducing redundancy and potential anomalies.
   • Aims for a higher level of data integrity and consistency.

4. Boyce-Codd Normal Form (BCNF)

   • A stronger version of 3NF that addresses certain types of anomalies not handled by 3NF.
   • Requires that for every functional dependency, the left-hand side must be a superkey.
   • Eliminates redundancy caused by overlapping candidate keys.
   • Ensures that all dependencies are based on the whole key, enhancing data integrity.

5. Fourth Normal Form (4NF)

   • Addresses multi-valued dependencies, where one attribute can have multiple independent values.
   • Requires that no table contains two or more independent multi-valued data describing the same entity.
   • Ensures that each piece of information is stored in its own table, reducing redundancy.
   • Aims to eliminate potential update anomalies related to multi-valued dependencies.

6. Fifth Normal Form (5NF)

   • Focuses on eliminating redundancy caused by join dependencies.
   • Ensures that every join dependency in the table is a consequence of the candidate keys.
   • Requires that data is split into smaller tables to avoid redundancy while still allowing for reconstruction through joins.
   • Aims for a highly normalized structure that maintains data integrity and minimizes redundancy.

7. Denormalization

   • The process of intentionally introducing redundancy into a database to improve read performance.
   • Often used in data warehousing and reporting scenarios where complex queries can be optimized.
   • Balances the trade-off between normalization (data integrity) and performance (query speed).
   • Can lead to increased storage requirements and potential data anomalies if not managed carefully.