Flex :: Datagrid Not Updated Properly?

I have two tables: Person {pID, pName, deptID} and Departments {deptID,deptName}An SQL statement like this gets me the name of a person and the department name:

SELECT pName, departments.deptName FROM people INNER JOIN people.deptID = departments.deptID;

The above works fine. I have a Flex DropDownList that is populated with deptNames. When I click the submit button, I am able to obtain the ID of the selected department without problem:

protected function button_clickHandler(event:MouseEvent):void
{
person.pName=pNameTextInput.text;
person.deptID=pDepartmentDropDownList.selectedItem.deptID; //ID of selected department obtained correctly.
if (person.pID == 0)

[code]....

From the comment above, I see that adding person will indeed add the attributes of the person object to the datagrid, except that one attribute is a foreign ID (deptID) from departments.