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

[Dane Springmeyer]

Stephen,

Try:

select astext(st_linemerge(ST_Collect(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;

Thanks works for me.

Dane


On Oct 7, 2008, at 2:38 PM, Stephen Woodbridge wrote:

> 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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