如何在SQL中的一个特定行中找到最少的非空列？

I am trying to find the lowest number in two columns of a row in the same table, with the caveat that one of the columns may be null in a particular row. If one of the columns is null, I want the value in the other column returned for that row, as that is the lowest non-null column in this case. If I use the least() function in MySQL 5.1:I am trying to find the lowest number in two co