Try something like this -
SELECT p1.ID, p1.ParentID, p1.PageName, p2.ID, p2.ParentID, p2.PageName
FROM Pages AS p1, Pages AS p2
WHERE p2.ParentID=p1.ID
AND p1.ParentID=0
I haven't tried it, but I think it's correct.
If it doesn't produce what you want post again including some sample data (take a small data dump from the table) and I'll have another go.
Good luck 😉