Answer by BobbyShaftoe for C++: How to deal with NULL values (e.g. from a database)?

From http://art-blog.no-ip.info/wikipp/en/page/ref_dbixx_row :

Function cols() returns number of columns in the row. isnull() returns if specific filed is null, using it's column number (starting from 1) or column name;

bool operator[] is just syntactic sugar for isnull().

In your question you stated you were using dbixx, so I have linked to their documentation. This will always be specific to the library you are using.