SQL - Regroup by subfield

I've got a problem with my SQL. I have a table (named "Regions") looking like this :

What I want to do is sorting this table wit开发者_JS百科h the sub_region "next" to the region. In this exemple, Québec (9) and Ontario (10) are sub region of Canada (7) so I want to get them right after Canada. I don't know if it's stupid or my SQL is too rusty but I don't find a way to do that.... By the way, the website that will use this DB is with CakePHP, if that can be of any help!(Behavior or other built-in module, I don't know).

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select s.id, s.name, r.*
from Regions r
left join Regions s
on s.id = r.sub_region
order by(coalesce(s.id, r.id), r.id)

edit: I modified the joined query, I haven't tried it, but would you give that a shot, I think that syntax should work for mysql