Iterative Query for Spatial Records - sql

Question

I have created following query in SQL Server
declare #x XML
set #x='<Dataset_Extent>
<EXTENT_TYPE>Bounding_Polygon</EXTENT_TYPE>
<Vertex>
<LON>66.91292909247741</LON>
<LAT>30.27001012181008</LAT>
<X>299232</X>
<Y>3350549</Y>
<COL>1</COL>
<ROW>1</ROW>
</Vertex>
<Vertex>
<LON>66.99456841960638</LON>
<LAT>30.27128639618252</LAT>
<X>307089.5</X>
<Y>3350549</Y>
<COL>15715</COL>
<ROW>1</ROW>
</Vertex>
<Vertex>
<LON>66.99700791329992</LON>
<LAT>30.1509623521339</LAT>
<X>307089.5</X>
<Y>3337207.5</Y>
<COL>15715</COL>
<ROW>26683</ROW>
</Vertex>
<Vertex>
<LON>66.91546772378466</LON>
<LAT>30.14969219541345</LAT>
<X>299232</X>
<Y>3337207.5</Y>
<COL>1</COL>
<ROW>26683</ROW>
</Vertex>
<Center>
<LON>66.9549932872921</LON>
<LAT>30.21048776638499</LAT>
<X>303160.75</X>
<Y>3343878.25</Y>
<COL>7858</COL>
<ROW>13342</ROW>
</Center>
</Dataset_Extent>';
declare #wkt varchar(8000);
select #wkt=CONVERT(varchar(7000),#x.query('distinct-values(
for $lon in /Dataset_Extent/Vertex/LON/text()
for $lat in /Dataset_Extent/Vertex/LAT/text()
return ($lon cast as xs:string?,$lat cast as xs:string?,","))
'));
--concatenate the word POLYGON
set #wkt='POLYGON(('+#wkt +'))';
print #wkt
This gives me the following output:
POLYGON((66.91292909247741 66.99456841960638 30.27128639618252 66.99700791329992 66.91546772378466 30.27001012181008,30.1509623521339 30.14969219541345))
Each Lon/lat pair is not in proper order, I required output in following format:
POLYGON((66.91292909247741 30.27001012181008,66.99456841960638 30.27128639618252,66.99700791329992 30.1509623521339,66.91546772378466 30.14969219541345,66.91292909247741 30.27001012181008))
The starting vertex Lon/Lat should also repeat at end to make polygon close.
What do I need to do this to fix the problems?

Answer 1

this will do the job...
DECLARE #wkt NVARCHAR(MAX)
SELECT #wkt = COALESCE(#wkt + ',' + char(13), '')
+ concat(convert(varchar, x.query('./LON/text()')),' ', convert(varchar,x.query('./LAT/text()')))
from #x.nodes('/Dataset_Extent/Vertex') as t(x)
select #wkt = COALESCE(#wkt + ',' + char(13), '')
+ concat(convert(varchar, x.query('./LON/text()')),' ', convert(varchar,x.query('./LAT/text()')))
from #x.nodes('/Dataset_Extent/Vertex[1]') as t(x)
set #wkt='POLYGON(('+#wkt +'))';
print #wkt
not exactly beautiful but i couldnt figure out how to subquery the first node... good luck! i try to avoid xpath as much as possible if i can :)

Answer 2

Shred the XML on /Dataset_Extent/Vertex and build the string using the for xml path trick.
declare #wkt varchar(8000);
set #wkt = 'POLYGON((' +
stuff((select ','+T.X.value('(LON/text())[1]', 'varchar(50)')+
' '+T.X.value('(LAT/text())[1]', 'varchar(50)')
from #x.nodes('/Dataset_Extent/Vertex') as T(X)
for xml path('')), 1, 1, '')+
','+#x.value('(/Dataset_Extent/Vertex/LON/text())[1]', 'varchar(50)')+
' '+#x.value('(/Dataset_Extent/Vertex/LAT/text())[1]', 'varchar(50)')+
'))';
Against a table it would look like this instead.
select 'POLYGON((' +
stuff((select ','+T.X.value('(LON/text())[1]', 'varchar(50)')+
' '+T.X.value('(LAT/text())[1]', 'varchar(50)')
from X.XMLData.nodes('/Dataset_Extent/Vertex') as T(X)
for xml path('')), 1, 1, '')+
','+X.XMLData.value('(/Dataset_Extent/Vertex/LON/text())[1]', 'varchar(50)')+
' '+X.XMLData.value('(/Dataset_Extent/Vertex/LAT/text())[1]', 'varchar(50)')+
'))'
from XMLFiles as X;