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FIX: "An item with the same key has already been added" error when you review a report in SSRS 2012 or 2014
Content provided by Microsoft
Applies to: Microsoft SQL Server 2012 Service Pack 1Microsoft SQL Server 2012 Service Pack 2SQL Server 2012 Reporting ServicesMicrosoft SQL Server 2014 Service Pack 1SQL Server 2014 Reporting ServicesMore
Assume that you have a report in Microsoft SQL Server 2012 Reporting Services (SSRS 2012) or in SSRS 2014 in SharePoint integrated mode. The report contains two datasets that connect to a SharePoint list. When you review the report, you may receive the following error message:
An error has occurred during report processing. (rsProcessingAborted) Query execution failed for dataset '<DatasetName>'. (rsErrorExecutingCommand) An item with the same key has already been added.
The issue was first fixed in the following cumulative update of SQL Server.
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