I am facing a problem in webservice, I want to know what will be the exact procedure to solve the problem.............

What I want to do............

I have a table named order in SQL Server. There are some fields including OrderID, DomainNameURL, SessionID. I want to create a webservice which takes a parameter(SessionID) and return the details from order table. Here OrderId works as a Unique key. but In some cases when SessionID is not a unique key (Two different domains can have same SessionID) my webservice fails. Now I want to pass the Url (which will be passed implicitly from the site where we will use the webservice) and SessionID(explicitly) in webservice. How can i do that...