[GRASSLIST:10144] Re: v.to.db option=query: issue with 2 layers and multiple categories

[Maciek Sieczka]

On Thu, 2 Feb 2006 09:41:10 +0100
Radim Blazek <radim.blazek at gmail.com> wrote:

Radim,

> Hi,
> I am satisfied to read that people are using and understand these
> more complex features in GRASS vector model.
> 
> I think (I hope) that the problem is that you have more cats
> (1,2) in the layer 1 on the point.

> If you use qcolumn=height v.to.db queries the database for this point
> with select height from testing_pt_nodupl2_1 where cat=1 or cat=2
> The result is 2 rows (100.5 twice). It is impossible to upload
> 2 values into one row in layer 2. If you have more cats in queried
> layer on the same geometry it is necessary to use an aggregate
> function, for example qcolumn=avg(height).
> 
> Does it work?



Right! There are indeed two categories in layer 1, for the same
geometry element. Now that you made me notice it it's obvious wy the
error, thanks.

However, there are _also_ two categories for the same geometry in layer
2 (10,11). I mean - I understand I couldn't upload 2 values into one
"row". But since in this particular case in both layer 1 and 2 there
are two "rows", isn't it somehow different? Just wondering.

Best,
Maciek

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