How to get weekly import files from one table to automatically associate to the parent file in another table.

Scenario/Context/Setup:

• Parent Table:  "Main Roster"
  
  • Key Field: Network ID
• Child Table:  "Anaplan Roster"
  • New file imported each week (does not override the previous)

How do I get it so that each week when the Anaplan Roster file is imported (child), it will automatically associate itself to the correct Main Roster record with the same Network ID (parent)?

Essentially, over time, I should be able to view multiple Anaplan Roster records under each associated Main Roster entry... and each week identify individuals missing in the Anaplan reports because they're in the Main Roster but not in Anaplan and/or identify any individuals who are incorrectly assigned to teams in Anaplan (thus have a running log for changes throughout the year).

Currently, I can't figure out how to get child to find its parent record automatically... it's requiring me to manually associate each Anaplan record to its parent record (even with grid edit, it's takes too much time as there are hundreds of people).   

Example: 

This seems like this should be a pretty easy thing to do, but for some reason I just can't figure it out... I very much appreciate any and all suggestions.

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Kristin
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