SELECT
a.mid_st,
a.geometry,
ST_Distance(geography(b.geometry), geography(a.geometry)) as distance
FROM
(
  SELECT DISTINCT ON (a.geometry)
  FROM public.ks2_st a
) as buildings
CROSS JOIN LATERAL
(
  SELECT b._mid_gji, b.geometry
  FROM gji.t2100_ill b
  ORDER BY a.geometry <-> b.geometry LIMIT 1
) as sewery