Identity by Ordered Subtraction

A number N consists of unique (all different) digits. Let A be the number formed by putting the digits in descending order. Let B be the number formed by putting the digits in ascending order. Find all possible N which satisfy A-B=N. (Leading zeros are allowed, if needed.)

Are there any additional answers if we remove the requirement that N consists of unique digits (but still be no more than 10 digits)?

Source: Based on a problem from Casio's Problem of the Week. Original extensions.


Solution
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