satu-ke-satu pembatasan yang berbeda pada seleksi

Coba:

select a.id, a.x as ax, b.x as bx, x.min_abs_diff
  from table_a a
  join table_b b
    on a.id = b.id
  join (select a.id, min(abs(a.x - b.x)) as min_abs_diff
          from table_a a
          join table_b b
            on a.id = b.id
         group by a.id) x
    on x.id = a.id
   and abs(a.x - b.x) = x.min_abs_diff

biola:http://sqlfiddle.com/#!15/ab5ae/5/0

Meskipun tidak sesuai dengan output yang Anda harapkan, saya pikir outputnya benar berdasarkan apa yang Anda jelaskan, karena Anda dapat melihat setiap pasangan memiliki perbedaan dengan nilai absolut 1.

Sunting - Coba yang berikut ini, berdasarkan urutan a hingga b:

select *
  from (select a.id,
               a.x as ax,
               b.x as bx,
               x.min_abs_diff,
               row_number() over(partition by a.id, b.x order by a.id, a.x) as rn
          from table_a a
          join table_b b
            on a.id = b.id
          join (select a.id, min(abs(a.x - b.x)) as min_abs_diff
                 from table_a a
                 join table_b b
                   on a.id = b.id
                group by a.id) x
            on x.id = a.id
           and abs(a.x - b.x) = x.min_abs_diff) x
 where x.rn = 1

Biola:http://sqlfiddle.com/#!15/ab5ae/19/0