Get all parent records for a child category - is good for getting the records for a breadcrumb trail. Thanks to http://stackoverflow.com/questions/2441821/getting-all-parent-rows-in-one-sql-query

parent-categories.sql

select t2.id, t2.name
from (
    select
        @r as _id,
        (select @r := parent_id from categories where id = _id) as parent_id,
        @l := @l + 1 as lvl
    from
        (select @r := :id, @l := 0) vars,
        categories h
    where @r <> 0) t1
join categories t2 on t1._id = t2.id
order by t1.lvl desc