you do not get an import spec when bringing in a spreasheet
the problem is two fold
1. access/excel guessdatatypes based on the first few rows of data, and often treat columns as numbers, when they should be text. one way to avoid this, is to insert a row 2, and put a word like "TEXT" in any coulmn that must be text
2. some cells may contain bad data.
the import errors table will show you the suspect rows, so that you can see what the problems are.
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a csv is always better to import than a spreadsheet, imo. you get more control, and general you know the file has not been "compromised". if you have a "raw data" csv, then use that instead of the spreadsheet. avoid the spreadsheet, as actually opening a csv in excel, and saving it again may change it
however if you have a xls file to start with, there is little point in going to the trouble of saving it as a csv.