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This will mean that we have Country as a common field for 2014 and 2013 so this will form our join when we add the Append.
Note: sometimes you will have a case where you don't wish to filter the Country list by 2014, this may be because some countries have no results for 2014 yet. In this case you would have Country in the Master Query, and an Append Query for each Invoiced Amount.
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