[postgis-users] How does makeline work?

[Mark Cave-Ayland]

> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net 
> [mailto:postgis-users-bounces at postgis.refractions.net] On 
> Behalf Of Guido Lemoine
> Sent: 09 September 2005 08:57
> To: PostGIS Users Discussion
> Subject: Re: [postgis-users] How does makeline work?
> 
> 
> Mark,
> 
> Thanks for the clarification.
> 
> I tried your suggestion, already as part of my original tests. Your 
> version gives
> a syntax error at the inner select statement inside makeline. 
> If I add 
> extra brackets
> to make it an expression, it returns the following error.
> 
> select astext(makeline((select gcp_geom from testset order by 
> gcp_id))) 
> from testset;
> ERROR:  more than one row returned by a subquery used as an expression
> 
> I didn't report this one, because I thought it was logical (similar 
> error for other aggregate
> functions). But now I am not so sure.
> 
> Guido


Hi Guido,

Sorry, I made a mistake when reading the documentation :) I've had a play on
a real database and the following should work better:


select astext(makeline(foo.gcp_geom)) from (select gcp_geom from testset
order by gcp_id) AS foo;

select astext(makeline(foo.gcp_geom)) from (select gcp_geom from testset
order by gcp_id desc) AS foo;

 
Kind regards,

Mark.

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