Surrogate vs Natural Keys in Warehouse Dimensions

By Tom Nonmacher

The choice between surrogate and natural keys in warehouse dimensions is one that can significantly impact the efficiency and effectiveness of your database management system. Before we delve into the specifics of each, it's important to understand that the choice of key types is highly dependent on the nature of your data and the specific requirements of your system. In this article, we'll explore both types of keys and provide some examples using SQL Server 2016, SQL Server 2017, MySQL 5.7, DB2 11.1, and Azure SQL.

Natural keys, also known as business keys, are data elements that naturally exist in the real world and are unique to each record in the database. They are often used in operational systems where data is directly linked to real-world entities. However, natural keys can present challenges in situations where they change over time, as updates to the key can cause cascading changes throughout the database.

Surrogate keys, on the other hand, are system-generated, arbitrary and do not have a business meaning. A typical example of a surrogate key is an auto-incrementing integer. Using surrogate keys can help avoid issues related to changes in natural keys, as they remain constant over time. Additionally, surrogate keys often lead to performance improvements in large databases due to their simplicity and uniformity.

Let's take a look at an example of creating a table with a surrogate key in SQL Server 2016. We will use the function IDENTITY to create an auto-incrementing integer that will serve as our surrogate key. 


CREATE TABLE Customers
(
  ID int IDENTITY(1,1) PRIMARY KEY,
  Name varchar(255) NOT NULL,
  Email varchar(255)
)

In contrast, here's an example of creating a table with a natural key in MySQL 5.7. In this case, we are using the customer's email address as the natural key. This assumes that each customer's email address is unique. 


CREATE TABLE Customers
(
  Email varchar(255) PRIMARY KEY,
  Name varchar(255) NOT NULL
)

In conclusion, the choice between surrogate and natural keys in warehouse dimensions depends on the specific needs and constraints of your system. While natural keys can offer more meaningful data relationships and easier data integration, surrogate keys can provide stability, simplicity, and performance improvements. Each approach has its merits, and the decision should be guided by a thorough understanding of your database system and its requirements.

We at SQLSupport.org are always here to provide guidance and support in making these critical decisions. Feel free to reach out to us with any questions or concerns about your database management system.

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