これを行うには、rankという名前の疑似列を各選択に追加します。これは、他の条件で並べ替える前に、最初に並べ替えることができます。例:
select *
from (
select 1 as Rank, id, add_date from Table
union all
select 2 as Rank, id, add_date from Table where distance < 5
union all
select 3 as Rank, id, add_date from Table where distance between 5 and 15
) a
order by rank, id, add_date desc