Postgres-从2个表中检测重叠的行

Question

问题：我有一张桌子，上面有一个国家（波兰）的自行车道和远足径。

Table bicycle_merge

way      | route  | name        |network    |osmc_color| state  
geometry | text   | text        |text       |text      | text
----------------------------------------------------------------
{geo1}   |bicycle |szlak1       |ncn        |blue      |proposed
{geo2}   |bicycle |szlak2       |lcn        |red       |null
{geo3}   |bicycle |szlak3       |ncn        |green     |proposed
{geo4}   |bicycle |szlak4       |rcn        |blue      |proposed
{geo5}   |bicycle |szlak5       |lcn        |blue      |null
{geo6}   |bicycle |szlak6       |ncn        |yellow    |proposed
....and so on

Table hiking_merge

way      | route  | name        |network    |osmc_color| state  
geometry | text   | text        |text       |text      | text
----------------------------------------------------------------
{geo1}   |hiking  |szlak1       |ncn        |blue      |proposed
{geo2}   |hiking  |szlak2       |ncn        |red       |null
{geo3}   |hiking  |szlak3       |ncn        |green     |proposed
{geo4}   |hiking  |szlak4       |ncn        |blue      |proposed
{geo5}   |hiking  |szlak5       |ncn        |blue      |null
{geo6}   |hiking  |szlak6       |ncn        |yellow    |proposed
...and so on

{geo1}，{geo2}等是每条步道的独特几何形状。

每条小径都有独特的几何形状，但有时自行车和远足路线会重叠。 下图显示了QGIS中的示例： 我想删除重叠的部分，因为我已经将它们放在另一个数据库中。

编辑：我尝试了茱莉亚·莱德（Julia Leder）建议的解决方案：

create table intersections as
(select st_intersection(b.way, h.way) as overlapping_section
from bicycle_merge b, hiking_merge h
where st_intersects(g.way, h.way));

并非所有重叠的线都被检测到。 我不确定为什么吗？ 这是一张显示问题的图片：

Answer 1

您在寻找这个吗？

(SELECT way,route,name,color,description,network FROM bicycle_merge
UNION
SELECT way,route,name,color,description,network FROM hiking_merge)
EXCEPT
(SELECT way,route,name,color,description,network FROM bicycle_merge
INTERSECT
SELECT way,route,name,color,description,network FROM hiking_merge);

这是MS SQL语法。 对于Oracle，编写MINUS而不是EXCEPT 。

Answer 2

select *
from
    (
        select *
        from bicycle_merge bm
        where not exists (
            select 1
            from hiking_merge
            where geometry = bm.geometry
        )
    )
    union
    (
        select *
        from hicking_merge hm
        where not exists (
            select 1
            from bicycle_merge
            where geometry = hm.geometry
        )
    )

Answer 3

使用PostGIS功能可以相对容易地做到这一点。 您需要找到两个几何之间的重叠部分，可以用

ST_Intersection(a.geometry, b.geometry)

然后，您需要从自行车或远足几何中的原始几何中减去该部分，具体方法是：

ST_Difference(a.geometry, b.geometry)

放在一起：

create table intersections as
(select st_intersection(st_buffer(b.way,10), st_buffer(h.way,10)) as overlapping_section
from bicycle_merge b, hiking_merge h
where st_intersects(st_buffer(g.way, 10), st_buffer(h.way,10)));


update bicycle_merge b 
set way = st_difference(b.way, overlapping_section)
from intersections where st_intersects(b.way, overlapping_section);

update hiking_merge h 
set way = st_difference(h.way, overlapping_section)
from intersections where st_intersects(h.way, overlapping_section);

可能需要根据几何类型以及如何存储它们进行某种程度的调整，但是以上所述应该可以为您提供帮助。

st_buffer函数的第二个参数采用缓冲区的半径。 此数字的单位取决于几何形状。 它们可以以英尺，米或度为单位，具体取决于几何图形的SRID，您可以通过以下方式检查

select st_srid(way) from biking_merge limit 0;