I had same issue and solved it by creating 2 tables in database, one called DATA and other called IMPORT
So I made it to import into IMPORT table and then update data in DATA table, after process is done, drop IMPORT table
Of course, added duplicate check
Also added select file, read column name and import to corresponding field so no matter where is column "First Name" it goes to field "First_name"
That is easiest you can do