SELECT
buildings.mid_st,
buildings.geometry,
ST_Distance(buildings.geometry::geography, sewery.geometry::geography) as distance
FROM
(
  SELECT DISTINCT geometry
  FROM public.ks2_st
) as buildings,
(
  SELECT _mid_gji, geometry
  FROM gji.t2100_ill
) as sewery
ORDER BY buildings.geometry <-> sewery.geometry
LIMIT 1