remove duplicate entries before export

[rinorway]

Following situation is happening quite often:

Contacts can be members of several groups.

So contact - -- membership ---- account

Membership = entitity , like Board, working group x , team y.

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• Question : give me a list of email adresses of board and team Y
• Approach : select contact.email from membership where membership is in (board, team y)
• Issue : duplicate entries in export ( eg john@doe.com is both member of board and team y)
• Suggestion : have a "Only unique records" in the xls export modal dialog, next to "Export all fields"