16.4.3 Closest Gaia EDR3 neighbour to each Gaia DR2 source

select floor(min_angular_distance) as angular_distance_bin,
  proper_motion_propagation, count(*) as n from (
  select dr2_source_id, min(angular_distance) as min_angular_distance
  from edr3.dr2_neighbourhood as xm
  join gaiadr2.gaia_source as gaia2
    on xm.dr2_source_id = gaia2.source_id
  where random_index < 10000000
  group by dr2_source_id
) as subquery
join edr3.dr2_neighbourhood as xm
  on subquery.dr2_source_id = xm.dr2_source_id
    and subquery.min_angular_distance = xm.angular_distance
group by proper_motion_propagation, angular_distance_bin
order by proper_motion_propagation, angular_distance_bin