Table: Null values do not sort correctly.

[samussiah]

Because null is neither less nor greater than any other value.

[jwildfire]

Where do we want null values? At the bottom in descending at at the top in ascending?

[samussiah]

First would make it obvious that there are null values. Last would make values you probably don't care about appear last. I don't know. Also, sorting fails when the underlying values are of different types, e.g. numeric and character, because sort doesn't coerce type.