Error 8672 in MS SQL 2008 while using Merge statement

This is one of the weird error you get in MS SQL 2008 if you have Merge statement in your query.

Below is the complete exception message which you may receive. 

The MERGE statement attempted to UPDATE or DELETE the same row more than once. This happens when a target row matches more than one source row. A MERGE statement cannot UPDATE/DELETE the same row of the target table multiple times. Refine the ON clause to ensure a target row matches at most one source row, or use the GROUP BY clause to group the source rows. [SQLSTATE 42000] (Error 8672).

Interesting thing about the above exception is you will get this exception even if you don’t have duplicate rows are there during the join operation. When I got this message I was checking for the duplicate rows first as the error message was highlighting that.

Any way Microsoft informed that this is a bug in SQL Server 2008. In order to resolve this issue you have to install Cumulative Update 6 for SQL Server 2008 Service Pack 1. You can download the same from Microsoft Download centre. Here is the link for “Cumulative Update 6 for SQL Server 2008 Service Pack 1”.

Microsoft created a KB article to address this issue. If you are interested to know more about this issue please refer Microsoft KB article.

I hope after installing the above updates your error is disappeared and the same query is running without any issues.