You will not have to write the file out to disk and re-consume it. Check out this link here: http://objectsharp.com/cs/blogs/matt/archive/2004/11/09/1009.aspx it gives you a few options when dealing with messages inside of your orchestration.
Is your ID element a repeatable node? If not then i would look into setting this element to be a distinguished field. That way once you have your response document you could then copy(use message assign shape) your request document and then update that field with the value from you SQL Response document.