sql - 空间数据查询

Question

我有以下查询，它与表进行自连接并输出线之间的所有交点。

insert into road_intersection
select nextval('road_intersection_id_seq'), a.road_id, b.road_id, st_intersection(a.road, b.road), st_centroid(st_intersection(a.road, b.road))
from polygon_road a, polygon_road b
where st_intersects(a.road, b.road) AND a.road_id!=b.road_id

但是它会为每个交叉点输出重复值，因为它会计算每条道路的交叉点。例如：

70;71;POINT_OF_INTERSECTION

71;70;POINT_OF_INTERSECTION

70AND71都是id两条不同道路的值。如您所见，对于相同的两条道路，交叉点已计算了两次。

有什么建议可以解决这个问题并且只计算一个交点？

Answer 1

尝试类似：

select nextval('road_intersection_id_seq'), 
       a.road_id, 
       b.road_id, 
       st_intersection(a.road, b.road), 
       st_centroid(st_intersection(a.road, b.road))
from polygon_road a, polygon_road b
where st_intersects(a.road, b.road) 
  --AND a.road_id!=b.road_id --not needed any more

  AND a.road_id < b.road_id

它将只留下一个十字路口（第一条道路ID较小的十字路口）