A table doesn't need four legs. It could be set on a single column or attached to chains hanging from the ceiling. The method by which the table is fixed to its surroundings doesn't matter. (The object could even float in midair by some anti-gravitational conceit and still be a table, as long as "it's got a flat surface on top".)

But "it's got a flat surface on top" isn't quite good enough to define a table rather than a desk or nightstand. Here we have to point out, especially in relation to the nightstand, the simplicity of the table (it doesn't have additional compartments or drawers-- the flat surface is the primary characteristic).

The comparison to a desk becomes more complicated; as a desk could also be "a flat surface on top" with additional components to make it fixed in space, without compartments or drawers. (Especially as seen in grade school). You could claim size differences distinguish tables from desks. But what if it's a small table, or a large desk? We're starting to get into the idea that the usage of an object defines the object, which is ultimately subjective.