Adding an entity key when no key is inferred from a view - entity-framework

Question

I have a database view which joins across a number of tables in SQL Server 2005. It looks something like this:
SELECT
m1.MenuName AS menu_name, m2.MenuName AS sub_menu_name, p.ProductName, od.amount
FROM
dbo.tblMenus AS m1
FULL OUTER JOIN
dbo.tblMenus AS m2
FULL OUTER JOIN
dbo.tblProductsRelMenus AS pm ON m2.Id = pm.SubMenuId ON m1.Id = pm.MenuId
FULL OUTER JOIN
(SELECT
dbo.tblOrderDetails.ProductId, SUM(dbo.tblOrderDetails.Ammount) AS amount
FROM
dbo.tblOrderDetails
FULL OUTER JOIN
dbo.tblOrders AS o ON dbo.tblOrderDetails.OrderId = o.OrderId
WHERE (o.OrderDestroyed = 0)
GROUP BY dbo.tblOrderDetails.ProductId) AS od
RIGHT OUTER JOIN
dbo.tblProducts AS p ON od.ProductId = p.ProductId ON pm.ProductId = p.ProductId
When I try to create an ADO .Net entity data model it complains about not having a primary key in the SSDL secion. I then found this:
http://msdn.microsoft.com/en-us/library/dd163156.aspx
but I don't understand the part about a defining query. Surely I just want a column with unique numbers to define the key, or?
<EntityType Name="SoldItemsView">
<Key>
<PropertyRef Name="SoldItemsViewId" />
</Key>
<Property Name="SoldItemsView" Type="int" Nullable="false" />
<Property Name="menu_name" Type="nvarchar" MaxLength="100" />
<Property Name="sub_menu_name" Type="nvarchar" MaxLength="100" />
<Property Name="ProductName" Type="nvarchar" MaxLength="50" />
<Property Name="amount" Type="int" />
</EntityType>
But how do I populate this column with unique numbers?
Thanks,
Barry

Answer 1

You can use only columns from the view. To define an entity key you must select column (or set of columns) from your view which uniquely identifies record from the view.