SQL Server 2008：基于ID的ST联合

Question

I have a table which contains spatial data (geography type). Let's call this table A. The table is structured as below:

AreaID  RegionID    RegionName  SP_Geography
---------------------------------------------
   1       1        EAST        *Geogstring*
   2       1        EAST        *Geogstring*
   3       2        NORTH       *Geogstring*
   4       2        NORTH       *Geogstring*
   5       3        WEST        *Geogstring*

From this table I want to update another table called table B. This table is structured as below:

RegionID    RegionNAme  SP_Geograph
-------------------------------------
1   EAST    *NULL*
2   NORTH   *NULL*
3   WEST    *NULL*

I want to use the STUnion command to combine the geography strings, and then update the empty SP_Geography column in Table B where the RegionID matches the RegionID in Table A.

I have managed to get the STUnion command to work between two individual rows (which successfully combines the two), but am not sure on how to use this to populate another table using a where clause or cursor.

Any help would be much appreciated!

Danny

PS I'm aware of the Union Aggregate function in SQL Server 2012, but I cannot use this as our databases have to run in 2008

Answer 1

What a quandary you find yourself in.....

I hope this little snippet of SQL will do the trick. Just make sure you change the regionID each time. If you want to make it dynamic simply put a cursor round the regionID and let the fun commence.

DECLARE @MergedGeog Geography
DECLARE @RegionID INt

SET @RegionID = 1

SELECT TOP(1) @MergedGeog=SP_GEOMETRY  FROM dbo.[SMA_Singapore_WGS84] WHERE RegionID = @RegionID

--perform the merge
SELECT @MergedGeog=@MergedGeog.STUnion(ISNULL(SP_GEOMETRY,@MergedGeog))
FROM (SELECT SP_GEOMETRY FROM  [SMA_Singapore_WGS84] WHERE RegionID = @RegionID) k

--return merged polygon

select @MergedGeog

Answer 2

UPDATE table B
SET SP_Geograph = CONCAT(a.SP_Geography1, isnull(a.SP_Geography2,''))
from
(SELECT a.RegionID, a.RegionName, a.SP_Geography as SP_Geography1, b.SP_Geography as SP_Geography2 from table a as a
left join table a as b on a.RegionID = b.RegionID and a.RegionName = b.RegionName) aa
where [table b].RegionID = aa.RegionID

Would this work? I haven't tested it.

UPDATE table B
SET SP_Geograph = SP_Geography1.STUnion(isnull(SP_Geography2,''))
from
(SELECT a.RegionID, a.RegionName, a.SP_Geography as SP_Geography1, b.SP_Geography as SP_Geography2 from table a as a
left join table a as b on a.RegionID = b.RegionID and a.RegionName = b.RegionName) aa
where [table b].RegionID = aa.RegionID

Or this...