When designing a database in SQL Server, one of the important decisions to make is choosing the appropriate data type for the primary key. In this article, we will discuss the pros and cons of using GUIDs and INTs as primary keys.

Size

GUIDs (Globally Unique Identifiers) are 16 bytes in size and can hold a vast number of values. On the other hand, INTs (integers) have varying sizes depending on the data type chosen. For example, a tinyint occupies 1 byte, a smallint occupies 2 bytes, an int occupies 4 bytes, and a bigint occupies 8 bytes.

It’s important to consider the size of the primary key column as it affects the space occupied by the table and the number of pages that need to be read for operations. Larger columns result in fewer records fitting in a page, leading to slower queries.

Uniqueness

GUIDs are considered to be universally unique, although not entirely true. They provide a high level of uniqueness, making them suitable for scenarios where uniqueness is crucial. On the other hand, INTs are only as unique as you make them. By adding a unique constraint or making the column a primary key, you can ensure uniqueness within the table. However, when comparing across tables or databases, there is no inherent uniqueness.

Portability

GUIDs are completely portable as they are universally unique. You can easily move values from one place to another without any issues. On the other hand, INTs with identity columns are not as portable. Merging tables with identity columns can be a cumbersome process, especially when dealing with different environments like production and testing.

Ease of Use

GUIDs require the use of functions like NEWSEQUENTIALID() or NEWID() to generate unique values. They need to be explicitly used during insert operations, as defaults, or as part of triggers. On the other hand, INT identity columns are created automatically and do not require any additional steps. They are generally easier to work with, especially if you have more experience using them.

Considerations

When deciding between GUIDs and INTs as primary keys, it’s important to consider the trade-offs. GUIDs offer high uniqueness and portability but come with larger storage requirements. INTs are easier to work with and have smaller sizes, but merging data with identity columns can be challenging.

Other factors to consider include the ease of debugging, the visual appeal of integers when displayed to end users, and the impact on you, your colleagues, and future developers who will work with the database.

Ultimately, there is no one-size-fits-all answer. The decision should be based on the specific requirements of your application and the trade-offs you are willing to make.

Remember, it’s important to think about the decision and not blindly follow a “one-size-fits-all” approach. Each scenario is unique, and the choice between GUIDs and INTs should be made after careful consideration.

Thank you for reading!