SQL Find difference between previous and current row

Question

I am trying to find the difference between the current row and the previous row. However, I am getting the following error message:

The multi-part id

Answer 1

See sqlFiddle

;WITH tblDifference AS
(
    SELECT ROW_NUMBER() OVER(ORDER BY id) AS RowNumber, columnOfNumbers 
    FROM tableName
)

SELECT cur.columnOfNumbers, cur.columnOfNumbers - previous.columnOfNumbers
FROM tblDifference cur
LEFT OUTER JOIN tblDifference previous
ON cur.RowNumber = previous.RowNumber + 1