To avoid blank values in imported data records, provide default values.
For new records, the default value is used if the source field is blank. For
existing records, the default value is used if both the source and target fields are
blank. If you use a lookup, decision tree, or decision table, the source value is the
value obtained from the lookup, tree, or table. It is not the value in the .csv
file.
What to do next: Select how to validate imported data. See Validating imported data.