[support] Sorting a table

Hi,

In one of my custom modules, I'm creating a table using theme('table', $header, $rows). The docs say that to sort the table, you should set 'field' to the database field on which to sort. What format should that database field be? I'm now entering for instance ...'field' => 'node.title'..., but that doesn't seem to work. I haven't seen an example module yet that uses this feature.

A second question: with the existing comment module, would I be possible to make comments for a specific node type only visible and editable for a certain user role, without affecting the comments for the other node types?

Thanks,

Thomas