How can i preload data from a database into the form

Unfortunately, this is not possible to achieve this inside of the form builder. 

If you have the programming resource, you can create a custom program using server side programming like PHP to create an interface/connection to pull data from your database to the form fields. You will also need to use the form's full source code then.

If you want to prepopulate fields, via URL parameters, you can achieve it according to the article mentioned on below URL:

https://www.jotform.com/help/71-Prepopulating-Fields-to-Your-JotForm-via-URL-Parameters

You may also use the app to generate a prepopulated form: http://prepopulate.jotform.io

If you need further assistance, feel free to revert back.