How to represent a data tree in SQL?

Question

I\'m writing a data tree structure that is combined from a Tree and a TreeNode. Tree will contain the root and the top level actions on the data. I\'m using a UI library to

Answer 1

Something like table "nodes" where each node row contains parent id (in addition to the ordinary node data). For root, the parent is NULL.

Of course, this makes finding children a bit more time consuming, but this way the actual database will be quite simple.