Hi Doreen,
Please email us for quicker response since sometimes we don't get to the forum until the weekend. :)
So long as the SharePoint libraries are on the same site, you don't need full trust.
If you are querying a database, why not just use DBXL's QueryDB? Then, you have a Web service and it's a piece of cake to dynamically query and it's domain trust.
If you insist on going the database query with the stock InfoPath data connection, and you are using the browser, please try to convert it to a UDCX and then change the UDCX credentials to specify a user who can access the DB. So long as the database is on the same server, it should work, but you may have to configure SSO credentials if its on a separate server.
If it's filler form, you shouldn't need full trust for any of this.
Need some more info, but rest assured, you should exit the forest with bread crumbs to spare shortly.