Yes, you should be able to do this. Part of the solution is to have a connection to the database. Lets talk about that in a minute. Then you will have for each dynamic question an area called advanced field options. In that area each field must be mapped to the dnn core with the 'quick create' link. Also there is a radio button for SQL options. If you click that you will see some text in the legend that is very important. It says:
"[L]Note: To enable SQL as a default value for textbox or hidden field types you MUST select only one column from the database and that column must be named DefaultValue. i.e. Select count(*) As DefaultValue from users" This text tells you how to set up a query for each field to pull data from the other database. Don't be literal like think you have to use count(*) that is just an example. You will be using Select 'field name' as Default value. . . Field name will be the other database table's field name that corresponds to the dynamic question in dynamic registration.
For connecting to your other database you will probably have something like this to implement in the web.config file or somewhere:
Note: '<' or '>' use your html to interpret. This place messes up correct html
<!-- Connection String for SQL Server 2005/2008 --><!-- --><!-- Connection String for SQL Server 2005/2008 - kept for backwards compatability - legacy modules -->
'<'!-- Connection String for SQL Server 2005/2008 --'>'
<'!-- Connection String for SQL Server 2005/2008 - kept for backwards
compatability - legacy modules --'>'
for Completion Events, use this:
Data Source=data.YourDataSource.com;Initial Catalog=YOURCATALOG;User ID=sa;Password=YOURPASSWORD
Hope this helps. If you need some help with this setup some small amount of premium support from DataSprings premium support should get you there.