sknox (9/24/2010)
So that gives us 2 identifier columns, remarkably similar to the two in this QotD -- and that's where you may have a point. But I'd caution here as well. First, we need to know why that surrogate UID is there.
No, this QotD only has one identifier:
OrderRefNo UNIQUEIDENTIFIER NOT NULL CONSTRAINT DF_OrderRefNo DEFAULT NEWID() CONSTRAINT PK_Order PRIMARY KEY CLUSTERED,
The other column, OrderNo, wouldn't qualify as a surrogate key or identifier in my book:
OrderNo INT NOT NULL IDENTITY(1,1),
The reason is there is no INDEX or CONSTRAINT that prevents duplicate values. Essentially is it just an INT field with a DEFAULT that creates sequential numbers, but someone can easily add rows with duplicate values.