如何将多个LineString行组合到单个行集合中

Question

我正在使用SQL Server 2008和Geometry数据类型存储英国道路列表,我从Ordanance Survey STRATEGI数据集导入.

每条道路被分成多行,每行包含一条线(A Linestring由一段组成).例如,A369由18条单独的线组成,如下图所示:

我想要做的是收集包含道路部分的所有单独行,并创建一个新行,将所有组合的单独行保存为一个线串.

换句话说,运行代码SELECT * FROM Structure WHERE Name = 'A369'只返回一行,但仍然绘制在上图中看到的道路.

Answer 1

只需使用.STUnion

BEGIN
-- create a test table
DECLARE @test TABLE(seg GEOMETRY);
INSERT INTO @test VALUES(geometry::STGeomFromText('LINESTRING (0 0, 50 100)', 0))
INSERT INTO @test VALUES(geometry::STGeomFromText('LINESTRING (50 100, 100 200)', 0))
INSERT INTO @test VALUES(geometry::STGeomFromText('LINESTRING (100 200, 150 300)', 0))
--SELECT seg.STAsText() FROM @test
DECLARE @geom GEOMETRY
SELECT @geom = (SELECT TOP 1 seg FROM @test)
-- union all the linestring points
SELECT @geom = @geom.STUnion([seg]) FROM @test
-- do what you want with the results
SELECT @geom
print(@geom.STAsText())
END