Beside the parent category, I would like to recursively collect all of its child rows.

(Pseudo code) `SELECT IDs FROM #_categories WHERE parent = father`

As an alternative, `SELECT IDs WHERE the first part of path is the parent's path`. 

Is this correct? What will be the most efficient way?

Even better:

Is there a standard method (probably in `ContentModelCategories`) to achieve what I need? Should I use `ContentModelCategories::getItems(true)`? How do I invoke it, given I already have the "parent" category ID?

A working example will be really appreciated.