- You have to build the DB in SQL first
- Create a web service to interact with it (read/write)
- Create a new, blank form that is browser-enabled and create data connections for submit and receive using your web service(s)
- Convert the data connections to UDC, which saves them in a Data Connection Library (MOSS only)
- Create a Single Sign-On entity in Central Admin for connecting from SharePoint to the SQL DB with an approved account
- Modify the UDC files from above to allow for the passage of the proper credentials (browser forms have double-hop issues with authentication)
The above is not simple and requires several different blog posts to piece together. Do you really need the data in a separate SQL DB? If you just save it directly to SharePoint, then that is still SQL, but you just don't have control of the table directly. For 5 fields, do you really need that? Keeping it in SharePoint as the DB would be 100 times easier.