How to Inert a Null Value to a column if there is not value to that column

I am inserting data from a text file into a tables.

In that Text file "first line" will have 7 values or 8 values.

For one DB, In First Line It may have 7 values or 8 Values. In DB i changed table that it has 8 columns.

If the file comes with 7 values i need to handle it to add 8 th value as NULL. How can i add?