There have already been five Cumulative Updates (CU) for the RTM branch of SQL Server 2012. Microsoft has also released SQL Server 2012 Service Pack 1, along with SQL Server 2012 SP1 Cumulative Update 1, with Cumulative Update 2 being due in the near future. There have been a high number of hotfixes in every one of these early Cumulative Updates, as more people are using SQL Server 2012 over time. Update: I have added information for SQL Server 2012 RTM CU5, which was released on December 17, 2012.
SQL Server 2012 SP1 has all of the fixes through SQL Server 2012 RTM CU2. If you have moved to the SP1 branch, you will want to get SQL Server 2012 SP1 CU1 so that you will have all of the same fixes as SQL Server 2012 RTM CU4.
This diagram of the post RTM builds might make this relationship more clear.
SQL Server 2012 RTM Branch Builds SQL Server 2012 SP1 Branch Builds
— 11.0.2300 RTM
— 11.0.2316 RTM CU1 4/12/2012
— 11.0.2325 RTM CU2 6/18/2012 –> 11.0.3000 SP1 RTM 11/7/2012
— 11.0.2332 RTM CU3 8/31/2012
— 11.0.2376 RTM CU3 + QFE 10/9/2012
— 11.0.2383 RTM CU4 10/15/2012 –> 11.0.3321 SP1 CU1 11/20/2012
— 11.0.2395 RTM CU5 12/17/2012 –>
You can follow the KB article links below to see all of the CU builds for the RTM branch and the Service Pack 1 branch.
Especially if you are getting ready to migrate to SQL Server 2012 from an earlier version, I think you should start out with the latest Service Pack and Cumulative Update. Right now, that means Build 11.0.3321, that will probably change next week.
Like I did in my previous post, I decided to scan the hotfix list for all of the Cumulative Updates in the RTM branch, looking for performance and general reliability-related fixes for the SQL Server Database Engine. I came up with the list below, but this is completely arbitrary on my part. You may come up with a completely different list, based on what SQL Server 2012 features you are using.
Again, the idea here is to give you some concrete reasons to want to stay current with the latest SP and CU, by pointing out some of the more valuable fixes in each CU.
SQL Server 2012 RTM Cumulative Update 1 (Build 11.0.2316)
SQL Server 2012 RTM Cumulative Update 2 (Build 11.0.2325)
SQL Server 2012 RTM Cumulative Update 3 (Build 11.0.2332)
SQL Server 2012 RTM Cumulative Update 4 (Build 11.0.2383)