create table metzger_merged as
  select ST_Intersection(
    case ST_IsValid(cntr_border.geom)
      when true then cntr_border.geom
      else ST_Buffer(cntr_border.geom, 0)
    end,
    case ST_IsValid(metzger.geom)
      when true then metzger.geom
      else ST_Buffer(metzger.geom, 0)
    end
  )
  from cntr_border, metzger;