Tree related problem

How to find the child and subchild of particular node in a tree in sql.

more data needed for intelligent answer..

my database is like this: { id name subject body root_id parent_id lft rgt depth created_at updated_at }

now what I want to do for the given id is I want to find all its children and sub children

I think this work

Tell me guys whether this is absolutely fine or not as I haven't checked it for all cases: