SQL Server-点几何中的线串

编程问答 2022-08-23

问题描述

是否有一种简便的方法可以在sql中的Points列之外创建Linestring？

例如，我有一个查询：

SELECT Geom FROM api.Table WHERE WellId = 'XYZ1234' ORDER BY MeasuredDepth ASC;

返回186点为wkb：

Geom
0xE6100000010CDEB06D5166275AC024B4E55C8A114440
0xE6100000010CE5F21FD26F275AC061FD9FC37C114440
0xE6100000010C4512BD8C62275AC0FCA5457D92114440
0xE6100000010CF33CB83B6B275AC063450DA661144440
0xE6100000010CA56B26DF6C275AC01E32E54350134440
0xE6100000010CBDFBE3BD6A275AC0C1CAA145B6134440
0xE6100000010CB6D617096D275AC03A92CB7F48134440
0xE6100000010CFD82DDB06D275AC04C4F58E201134440
0xE6100000010C9A081B9E5E275AC0041C42959A114440
...

我还可以将这些wkb保存在临时表中，并将其作为文本返回：

POINT (-104.61562 40.137035)
POINT (-104.6162 40.13662)
POINT (-104.61539 40.137283)
POINT (-104.61592 40.15923)
POINT (-104.61602 40.150887)
POINT (-104.61589 40.154)
POINT (-104.61603 40.15065)
POINT (-104.61607 40.148495)
POINT (-104.61515 40.13753)
POINT (-104.61605 40.15017)
...

但是从MSSQL documentation中，我找不到从所有这些点中制作Linestring的任何方法。这是否可能，例如PostGIS ST_MakeLine之类的东西？

解决方法

您可以将Geom列的X和Y属性连接到一个字符串变量中，然后将LINESTRING与该变量中包含的所有点一起使用。

    declare @string varchar(max)

    Select @string = isnull(@string + ',','') + cast(Geom.STX as varchar(20)) + ' ' + cast(Geom.STY as varchar(20))
    from api.Table

    Set @string = 'LINESTRING(' + @string + ')';   

    Select geometry::STLineFromText(@string,4326);
,

接受的答案正是我所要的，但是它会失去升序（基于另一个变量）吗？将其作为输出：

LINESTRING (-104.615 40.1378,-104.615 40.1378,-104.615 40.1377,-104.615 40.1376,...)
,

为订购问题添加第二个答案，您可以遍历带有标识列的表。

在下面的示例中，我将创建一个具有ID标识的表变量，将记录插入该表中，然后迭代并填充字符串。

    declare @points table (Id int identity,Geom geometry)

    Insert into @points (Geom)  
    SELECT Geom 
    FROM api.Table 
    WHERE WellId = 'XYZ1234' 
    ORDER BY MeasuredDepth ASC;

    declare @iterRow    int,@rowCount   int,@string     varchar(max),@x          varchar(20),@y          varchar(20)

    Select  @iterRow = 1,@rowCount = count(1)
    from @points

    While (@iterRow <= @rowCount)
    Begin   
        Select  @x = cast(Geom.STX as varchar(20)),@y = cast(Geom.STY as varchar(20))
        From @points
        where Id = @iterRow
        
        Set @string = isnull(@string + ','') + @x + ' ' + @y

        Set @iterRow += 1
    End

    Set @string = 'LINESTRING(' + @string + ')';   

    Select geometry::STLineFromText(@string,0);
multilinestringpointsql-server