Comparing SELECT Performance of Joining Integers vs GUIDs in SQL Server
Overview There are plenty of online conversations and articles asking which makes a better primary key: INT or GUID? There are pros and cons to both, but from my perspective the winner is INT by a small margin. As shown in this article , as long as the indexes are maintained to keep fragmentation down the performance is similar, with INT slightly ahead in both index size and the speed of CRUD operations. The key is storing the GUID as a UNIQUEIDENTIFIER datatype and never using VARCHAR. Not only is SQL Server less efficient at comparing strings, there's also a chance to run into collation issues comparing across databases. In these discussions, one thing I haven't seen is a comparison of SELECT performance when joining different datatypes. After all, it's rare to find queries that don't stretch across multiple tables in a relational database. I used the StackOverflow2013 database (83 GB size) for testing. Download a copy for yourself from Brent Ozar's fanta...