[postgis-users] ST_UNION(linestring, linestring) returns a multilinestring

[Stephen Woodbridge]

This does not seem to work. Am I using it wrong?


select astext(st_linemerge(b.the_geom))
   from (
     select ST_GeomFromText('LINESTRING(35.5269251710001 
33.891749555,35.527091166 33.8917984710001)') as the_geom
    union
    select ST_GeomFromText('LINESTRING(35.527091166 
33.8917984710001,35.5274352000001 33.8918998510001,35.528236559 
33.8919810230001)') as the_geom
   ) as b;
                                                   astext 

-----------------------------------------------------------------------------------------------------------
  LINESTRING(35.5269251710001 33.891749555,35.527091166 33.8917984710001)
  LINESTRING(35.527091166 33.8917984710001,35.5274352000001 
33.8918998510001,35.528236559 33.8919810230001)
(2 rows)

The results that I am expecting to get are:

  LINESTRING(35.5269251710001 33.891749555,35.527091166 
33.8917984710001,35.5274352000001 33.8918998510001,35.528236559 
33.8919810230001)

-Steve


Fred Lehodey wrote:
> =>   ST_LineMerge()
> Fred.
> On Tue, Oct 7, 2008 at 8:58 PM, David William Bitner <bitner at gyttja.org 
> <mailto:bitner at gyttja.org>> wrote:
> 
>     Check out ST_Merge()
> 
> 
>     On Tue, Oct 7, 2008 at 3:54 PM, Stephen Woodbridge
>     <woodbri at swoodbridge.com <mailto:woodbri at swoodbridge.com>> wrote:
> 
>         Hi all,
> 
>         This is very annoying. I have two linestrings the join
>         end-to-end and I want to build a new single linestring by
>         merging the two. How can I do this?
> 
>         Thanks,
>          -Steve
> 
> 
>         select astext( ST_Union(      
>          ST_GeomFromText('LINESTRING(35.5269251710001
>         33.891749555,35.527091166 33.8917984710001)'),
>         ST_GeomFromText('LINESTRING(35.527091166
>         33.8917984710001,35.5274352000001 33.8918998510001,35.528236559
>         33.8919810230001)')                                    ));
> 
>                      astext
>         --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>          MULTILINESTRING((35.5269251710001 33.891749555,35.527091166
>         33.8917984710001),(35.527091166
>         33.8917984710001,35.5274352000001 33.8918998510001,35.528236559
>         33.8919810230001))
>         (1 row)
> 
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> 
>     -- 
>     ************************************
>     David William Bitner
> 
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