Perhaps you're having trouble finding such an example because a generic solution would be too complex to put on a blog, and anything else would be too case-specific. The general steps to accomplish what you want are:
- Receive the XML as a string and load it into an XmlDocument object. Create a corresponding XmlNamespaceManager object to handle the namespaces.
- Create an SqlConnection to your database and use an SqlCommand that will perform the insert.
- Iterate through the nodes in the XML document, executing an SqlCommand with each set of data.
The above assumes you don't need to enforce any sort of permissions at the server, or modify the values in the database using InfoPath afterwards.
If, given the above steps, you still can't figure out how to accomplish the task without someone handing you the code, then the question is - How do you intend to maintain the code? (and it will need maintaining).
Part of making good business solutions is knowing what's already out there so you don't waste time and money reinventing the wheel. Qdabra has spent thousands of man-hours developing a product that does exactly what you want to do (and more), and is offering it to you at a rock-bottom price. When you consider the amount of time and money your company has already spent on your searching for a special-case, single-use approach, it's not that hard to see that the smart money is with DBXL.