I have a requirement to convert all our current Word based forms to a web based format to allow users to submit via our Intranet.I am looking at using InfoPath 2010 with SharePoint 2010 to do this.The form data needs to be stored in SQL Server database and the forms will need at least 2 levels of approval (Workflow) I've created test forms and submitted to SQL directly from InfoPath without SharePoint without a problem, I've also managed to submit form to SharePoint and the form data was stored as XML. What I am stuggling with is to get the form data into SQL and, simultaneously get it published to SharePoint so that the approval workflow can be setup. I've been looking how to do this but there appear to be so many possible various methods I'm not sure where to start.
Usually for this kind of requirement, I personally go for writing WCF based service for performing all SQL Server activities and use Entity Framework 4 to ease your life with database!
And then use InfoPath forms and on submit action call the WCF Service from InfoPath to insert data into the database...
Now bringing data into SharePoint 2010 can be done using Business Connectivity Services [BCS], making external content types for your tables and then External Lists..
NOTE: But there is a limitation for External Lists that SharePoint Workflows do not work on External Lists...
Also, here is the QUESTION ALREADY ASKED contains Expert's suggestions
I hope this helps, and let me know if you need more help...