From v1.7+ NSurvey is introducing a new model called "publisher / subscriber".

 In some scenarios it might be very useful to have more information about the users who are taking your forms. NSurvey provides several ways to gather external information from the users.

Sql based query answer types are another powerful feature of Survey. Using Sql based type you can expose and use existing data directly in your survey.
 

In some scenarios allowing select queries against a database can be a security threat. By default all nsurvey administrator can create / change sql based type.  

Here is a little tip on the usage of the active checkbox in the survey settings. Most of you might be wonder what this checkbox is for. 

We would like to port Survey onto our corporate Oracle data base, but we need to write our own data access layer (something like Votations.NSurvey.OracleDAL.dl

 When you create a form you can insert user's answers into the text of questions, answer choices or as a default text infield type answer.

 List of QUERIES to create an overview of one survey/users/questions/answers details. Should give you some idea of what database tables to use.

Basic querie sample of how to extract Survey Answers from Survey Database