Question

这两个查询之间有什么区别：

select a.gid, sum(length(b.the_geom)) 
  from polygons as a 
     , roads as b 
 where st_intersects(a.the_geom,b.the_geom) 
 group by a.gid ;

select a.gid, sum(length(b.the_geom)) 
  from polygons as a 
     , roads as b 
 where st_overlaps(a.the_geom,b.the_geom) 
 group by a.gid ;

第一个查询提供正确的输出，而第二个查询根本不检索任何行。与多边形相交的道路也与它重叠，对吗？

Answer 1

来自PostGIS的文档

http://postgis.net/docs/ST_Intersects.html

如果几何体或地理位置共享任何空间部分，则它们相交。重叠，触摸，在所有暗示空间交叉。如果有的话上述返回为真，那么几何也在空间上相交。

http://postgis.net/docs/ST_Overlaps.html

如果Geometries＆＃34;在空间上重叠＆＃34;则返回TRUE。我们的意思是它们相交，但一个不完全包含另一个。

不同之处在于：如果两个几何重叠100％，则它们不再重叠。

这是一个POSTGIS示例：

SELECT ST_Overlaps(a,b) As a_overlap_b, ST_Intersects(a, b) As a_intersects_b, ST_Contains(b, a) As b_contains_a
FROM (SELECT 
    ST_Polygon(ST_GeomFromText('LINESTRING(1 1,3 1,3 3,1 1)'), 4326)  As a,
    ST_Polygon(ST_GeomFromText('LINESTRING(1 1,3 1,3 3,1 1)'), 4326)  As b)
    As foo;
    -- INTERSECT is TRUE, OVERLAP is FALSE because B equals A

    SELECT ST_Overlaps(a,b) As a_overlap_b, ST_Intersects(a, b) As a_intersects_b, ST_Contains(b, a) As b_contains_a
FROM (SELECT 
    ST_Polygon(ST_GeomFromText('LINESTRING(1 1,3 1,3 3,1 1)'), 4326)  As a,
    ST_Polygon(ST_GeomFromText('LINESTRING(1 1,4 1,4 4,1 1)'), 4326)  As b)
    As foo;
    -- INTERSECT is TRUE, OVERLAP is FALSE because B contains A

    SELECT ST_Overlaps(a,b) As a_overlap_b, ST_Intersects(a, b) As a_intersects_b, ST_Contains(b, a) As b_contains_a
FROM (SELECT 
    ST_Polygon(ST_GeomFromText('LINESTRING(0 0,2 0,2 2,0 0)'), 4326)  As a,
    ST_Polygon(ST_GeomFromText('LINESTRING(1 1,3 1,3 3,1 1)'), 4326)  As b)
    As foo;
    -- INTERSECT is TRUE, OVERLAP is TRUE because not all of A intersects B and not all of B intersects A

st_intersects与st_overlaps

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