Showing posts from February, 2014

Why GUIDs Are a Bad Choice for SQL Server Key and Identity Columns

I've spent many years debating with my fellow developers across all manor of subjects (I do love to talk), but one subject that comes up time and time again is the usage of the UNIQUEIDENTIFIER data type in SQL Server; especially when they're used as identity and key columns. In fact, I see this more often than you would expect, and misconfigured UNIQUEIDENTIFIER columns can create "hidden" problems that can be difficult to discover and / or rectify, depending on the SQL experience throughout your team. If you care to ask around your colleagues, it's almost guaranteed that you'll get multiple conflicting opinions on why you should or should not use GUIDs in SQL Server, but few developers actually realise the impact of such a design choice. In the interests of science, I'll try and keep this as factual as possible, and I'll focus on the topic at hand, rather than GUIDs / UUIDs in general. Here's a list of common reasons for using a GUID in your d