How to insert the value NULL in a row?

[gpaddis]

I need to set the value NULL in a row in core_config_data (Magento 1.9). However, I tried with the values "null", "NULL", 0, I left the field blank: in all cases, the value in the database is either a string (an empty string, if I leave the field blank) or an int.

Is there a way to just insert NULL? What should I write in the CSV file?

[gpaddis]

I propose a solution for this issue in PR #21.