I would suggest you to use BCP utility to perform an import/export of data to a text file in SQL Server. When you run below command, it loads data to a text file.
BCP Db.TN out "Location of the text file " -c -S ServerName –T
Now if you want to load data to SQL Server from a flat file, you can use this:
BCP Db.TN in "Location of the text file " -c -S ServerName –T
You can also try editing Mappings while loading data from a flat file.