如何在两个几何表上进行UNION？

Question

我尝试：

  SELECT 
  ,6 AS ObjectTypeId
  ,[GeomColumn] AS geom
  FROM [dbo].[myTable1]

  UNION

  SELECT 
  ,objTyleId AS ObjectTypeId
  ,[GeomColumn] AS geom
  FROM [dbo].[myTable2]

但是出现了错误：

The data type geometry cannot be used as an operand to the UNION, INTERSECT or EXCEPT operators because it is not comparable.

是否存在用几何列合并表的另一种方法？

Answer 1

有两种方法，

1）使用UNION ALL替代UNION，

我们知道它们之间是有区别的，但也许可以满足您的需求。

2）使用CAST功能转换geometry为varbinary(MAX)

接下来：

Create table #myTable1 (ObjectTypeId int identity , GeomColumn geometry)
Create table #myTable2 (ObjectTypeId int identity , GeomColumn geometry)

INSERT INTO #myTable1 (GeomColumn)  
VALUES (geometry::STGeomFromText('LINESTRING (100 100, 20 180, 180 180)', 0));  

INSERT INTO #myTable2 (GeomColumn)  
VALUES (geometry::STGeomFromText('LINESTRING (100 100, 20 180, 180 180)', 0));  


select 1 AS ObjectTypeId , Cast( GeomColumn as varbinary(MAX)) geom 
from #myTable1
union 
select ObjectTypeId ,  Cast( GeomColumn as varbinary(MAX)) geom 
from #myTable2


Drop table #myTable1
Drop table #myTable2

结果：（一条记录通过使用显示UNION的是避免dublicated记录）