26 May, 2024 - About 1 minute
Database Normalization
Intro
Was watching this interesting video about Normalization. This article consolidates the Normal Forms rules.
Databases Normal Forms
First Normal Form (1NF)
- Using row order to convey information is not permitted.
- Mixing data types within the same column is not permitted.
- Having a table without a primary key is not permitted.
- Repeating groups of data on a single row is not permitted.
Second Normal Form (2NF)
- Each non-key attribute in a table must depend on the entire primary key.
Third Normal Form (3NF)
- Each non-key attribute in a table must depend on the key, the whole key, and nothing but the key.
Boyce-Codd Normal Form (BCNF)
- Each attribute in the table must depend on the key, the whole key, and nothing but the key.
Fourth Normal Form (4NF)
- The only kinds of multivalued dependency allowed in a table are multivalued dependencies on the key.
5NF
- It must not be possible to describe the table as being the logical result of joining some other tables together.
Note that the Normal forms are cumulative which means 5NF must bind also to 4NF,3NF and so forth.
Why is this important
Normalization entails organizing the columns (attributes) and tables (relations) of a database to ensure that their dependencies are properly enforced by database integrity constraints.
Conclusion
This article summarizes the several Normal forms that you encounter in Database Normalization and it’ s characteristics. If you would like to learn more about the topic I would advise watching the Decomplexity video as the author did a great job explaining with examples.