My suggestion is to upload the file to a special table in your app for uploads. his is a temporary scratchpad table where you can make various report to scrub your data and prepare it for import. Then have a button to import from he scratchpad to the real table.
for example that table can have Summary reports sorted on the Unique fields to sort them up to the top to be dealt with manually. If the non unique values are true duplicates, you can make a summary report off the scratchpad table and use the More ... button to copy these record to another table.
------------------------------
Mark Shnier (YQC)
Quick Base Solution Provider
Your Quick Base Coach
http://QuickBaseCoach.commarkshnier2@gmail.com
------------------------------