Database Normalisation Questions Long
Database normalization is a process that helps in organizing data in a relational database to eliminate redundancy and improve data integrity. It involves breaking down a database into multiple tables and establishing relationships between them. The normalization process is divided into different normal forms, each addressing a specific level of data redundancy and dependency. The different normal forms are as follows:
1. First Normal Form (1NF):
The first normal form requires that each column in a table contains only atomic values, meaning that it should not contain multiple values or sets of values. It eliminates repeating groups and ensures that each attribute has a single value.
2. Second Normal Form (2NF):
The second normal form builds upon the first normal form by ensuring that all non-key attributes are fully dependent on the primary key. It means that each non-key attribute should depend on the entire primary key, rather than just a part of it. This eliminates partial dependencies and improves data integrity.
3. Third Normal Form (3NF):
The third normal form further refines the database design by eliminating transitive dependencies. It requires that all non-key attributes are dependent only on the primary key and not on other non-key attributes. This helps in reducing data redundancy and improves data consistency.
4. Boyce-Codd Normal Form (BCNF):
The Boyce-Codd normal form is an extension of the third normal form and is used to handle more complex dependencies. It ensures that for every non-trivial functional dependency, the determinant is a candidate key. BCNF eliminates all non-trivial dependencies and guarantees that the database is free from anomalies.
5. Fourth Normal Form (4NF):
The fourth normal form deals with multi-valued dependencies. It requires that no non-key attribute is dependent on a combination of other non-key attributes. This helps in eliminating redundancy and ensures that each attribute is functionally dependent on the primary key.
6. Fifth Normal Form (5NF):
The fifth normal form, also known as Project-Join Normal Form (PJNF), deals with join dependencies. It ensures that a database is free from join dependencies by decomposing the database into smaller tables. This helps in maintaining data integrity and reducing redundancy.
Each normal form builds upon the previous one, with higher normal forms providing more strict rules for data organization. By following the normalization process and achieving higher normal forms, databases can be designed to efficiently store and retrieve data while minimizing redundancy and maintaining data integrity.