If the number of columns isn't the same or the names of the fields are not exactly the same then Qlikview will create two tables and create a synthetic key using all the fields that are the same. Keep in mind that Qlikview is case sensitive. That means the MyField and Myfield are two different fields to Qlikview. There's a good chance that the names of the fields of your two excel files are not completely the same. That's something you could check. And if necessary rename fields in the script using the as keyword (i.e. Myfield as MyField).