Please try this:
It is more simple than yours
GetOrders1 - Method in Webservice
OrderID - Parameter of Webserice.
ElementPath- Type exact column name in Database
<Query>
<SoapAction>http://tempuri.org/GetOrders1</SoapAction>
<Method Name="GetOrders1" Namespace="http://tempuri.org/">
<Parameters>
<Parameter Name="OrderID" type="int">
<DefaultValue>
10250
</DefaultValue>
</Parameter>
</Parameters>
</Method>
<ElementPath IgnoreNamespaces="true">GetOrders1Response{}/GetOrders1Result{}/diffgram{}/NewDataSet{}/Table{OrderID, ShipName, OrderDate,EmployeeID, RequiredDate}</ElementPath>
</Query>
I have checked and work