A special NULL value is a special
data type and is the result of arithmetic operations that lead to an overflow or a division by 0.The special NULL value is only permitted for output columns and for columns in the
ORDER clause. If an overflow occurs in an arithmetic operation or a division by 0 at another point, the SQL statement is abnormally terminated.The comparison of a special NULL value with any value is always undefined.
As far as sorting is concerned, the special NULL value is greater than all non-NULL values, but less than the
NULL value.