Do you mean the data in the rows or the columns is duplicated?
Same as: are there duplicate records, or duplicate fields?
Sorry I did not make it clear, it was duplicate records, looks like this
In sheet a:
In sheet b:
now I want to import those two columns from two sheets to one field in FMP database, how can I avoid duplicate records?
I don't think you can import using IWP.
But, otherwise, you could set a validation on the Factory field, and make it 'Unique' and to Validate Always. Then when you import the second table's duplicates they will not import.
Delete column A and C from the second Excel spreadsheet.