I was asked yesterday if it was “OK” to install SQL Server 2008 R2 on a system that already had SQL Server 2008, but without upgrading. In other words, they wanted to keep both versions of SQL Server running at the different levels. That’s supported; and it’s called a “side-by-side” installation. that means you’ll end up with at least one “Named Instance”, one at the first version and the other at the newer version. Everything is kept separate.
Well, not *everything*. While the engine, databases and all those kinds of things will still have separate versions, there are things that will be upgraded no matter what – it’s just a consequence of the upgrade. The list of things that will get a single, new version for SQL Server 2008 R2 when upgrading from 2008, for instance, from Books Online reads like this:
SQL Server Browser
SQL Server Active Directory Helper Services
SQL Server Profiler
SQL Server Native Client
SQL Server Policies
SQL Server System CLR Types
SQL Server VSS Writer
Business Intelligence Development Studio
Client tools connectivity
Client tools SDK
SQL Server Books Online
SQL Client Connectivity SDK
So it’s important to keep that in mind. There’s a topic similar to that link for 2005 in the Books Online for 2008, so you can see what will change if you make that upgrade as well. By and large it’s that same list.
You will see a difference from 2000, however, since some of these tools don’t exist on that older platform. In that case, you may end up with a bit of a mix – you’ll still have Enterprise Manager running around, for instance.
Installations and upgrades can be a difficult topic, but as long as you take your time and read through the installation planning documentation, you can write out the notes for what applies to you.