I assume you're talking about CSV file format, since your title refers to it. CSV files can't contain NULL values. The standard describes no way to express NULL in that format. The standard is described here: <https://tools.ietf.org/html/rfc4180> see also <https://en.wikipedia.org/wiki/Comma-separated_values> By all means, invent your own file format, encode NULL however you want, and write your own importer. In most of the computing languages I use, the NULL value is considered to be different to the empty string "", just as you say.