Denormalization
Overview
In the field of database management systems, denormalization is a strategy used to improve the read performance of a database at the expense of losing some write performance. Denormalization involves adding redundant data to tables or grouping data in a way that contradicts the rules of normalization.
Understanding Denormalization
Denormalization is a database optimization technique that is used to increase the performance of a database infrastructure. It involves increasing redundancy and duplication by creating groups of data, which can help to avoid costly database operations such as joins and queries. While normalization aims to minimize redundancy and keep data consistent, denormalization does the opposite, accepting redundancy to improve performance.
When to Use Denormalization
Denormalization is not a technique that should be used in all situations. It is typically used when specific data needs to be accessed quickly and frequently. It is also used when there are complex queries that involve multiple tables and joins, and the performance of these queries is critical. However, denormalization should be used judiciously, as it can lead to data anomalies and increase the storage space required for the database.
Advantages of Denormalization
Denormalization has several advantages. The primary benefit is that it can significantly improve the performance of read-heavy applications. By reducing the need for complex joins and queries, denormalization can make data retrieval faster and more efficient. This can be particularly beneficial in large databases where performance can be a significant issue.
Disadvantages of Denormalization
While denormalization can improve read performance, it comes with several disadvantages. One of the main disadvantages is that it can lead to data anomalies. Because denormalization involves duplicating data, there is a risk that the data could become inconsistent if it is not properly managed. Another disadvantage is that denormalization can increase the storage space required for the database.
Denormalization Techniques
There are several techniques that can be used to denormalize a database. These include:
- Prejoining: In this technique, frequently joined tables are permanently joined and stored in the database. This can reduce the need for costly join operations.
- Adding Redundant Data: This technique involves adding redundant data to a table to avoid complex queries.
- Adding Derived Attributes: This technique involves adding attributes that are calculated from other attributes to a table. This can avoid the need for costly calculations.
Conclusion
Denormalization is a powerful technique that can significantly improve the performance of a database. However, it should be used judiciously, as it can lead to data anomalies and increase the storage space required for the database. When used correctly, denormalization can be an effective tool in a database administrator's toolkit.