Removing duplicates in calculated column

Hi I want to create my own key between two datasets by adding first, last name and country (=FIRST&LAST&COUNTY). To be able to link together I would need to remove duplicates in one of the tables.

How do I do that?, Normally I would do it in the query editor, but its not visible in there.. can I do it in another way? or do I do something wrong

Thanks

Kristoffer