Question

I have recently started a new job and noticed that all the SQL tables use the GUID data type for the primary key.

In my previous job we used integers (Auto-Increment) for the primary key and it was a lot more easier to work with in my opinion.

For example, say you had two related tables; Product and ProductType – I could easily cross check the ‘ProductTypeID’ column of both tables for a particular row to quickly map the data in my head because its easy to store the number (2,4,45 etc) as opposed to (E75B92A3-3299-4407-A913-C5CA196B3CAB).

The extra frustration comes from me wanting to understand how the tables are related, sadly there is no Database diagram 🙁

A lot of people say that GUID’s are better because you can define the unique identifer in your C# code for example using NewID() without requiring SQL SERVER to do it – this also allows you to know provisionally what the ID will be…. but I’ve seen that it is possible to still retrieve the ‘next auto-incremented integer’ too.

A DBA contractor reported that our queries could be up to 30% faster if we used the Integer type instead of GUIDS…

Why does the GUID data type exist, what advantages does it really provide?… Even if its a choice by some professional there must be some good reasons as to why its implemented?

Answer 1

GUIDs are good as identity fields in certain cases:

• When you have multiple instances of SQL (different servers) and you need to combine the different updates later on without affecting referential integrity
• Disconnected clients that create data – this way they can create data without worrying that the ID field is already taken

GUIDs are generated to be globally unique, which is why they are suited for such scenarios.