There are several methods for linking forms and databases.

Sending data on form redirection and using hidden fields.

How to transfer data between two forms

Generate relational forms by retrieving submitted data and allowing your audience to choose from it.

How to lookup the submitted data of another form

URL parameters pass data in a link. Use them to autofill audience info, track metrics in Google services, or employ Facebook's conversion API.

How to use URL parameters to pre-fill form fields