In a nutshell: _base_question_data table stores users' answers to profile questions.
Structure
id – automatically generated sequence number for each row.
questionName – profile question name.
userId – integer number assigned to each user in _base_user database table.
textValue – value entered by user for profile questions of text type.
intValue – integer value selected by user for profile questions of select/fselect/multiselect type. Available values are stored in base_question_value database table.
dateValue – value selected by user for profile questions of datetime type.