[IPT] use of extensions; how can duplication of rows be avoided?

[Tim Robertson [GBIF]]

Hi Gabe,

You create 2 sources (both will point to the same database in your instance) and each will have a different SQL statement.  

It is probably not noticed, but with an IPT you can actually do things like connecting to a postgres database for specimens, and connecting to a mysql database for images provided there are shared unique identifiers in use that effectively do cross database joins.  That is pretty advanced usage, but is likely to crop up.  Similarly you can upload a CSV file and mix that in with a database connection.

Cheers,
Tim

On Oct 23, 2013, at 2:34 PM, Dröge, Gabriele wrote:

> Hi Tim,
>  
> Ok, but I am already using such views. How can I use multiple sqls in IPT? E.g. those two you suggested. Do you want me to put them all together in the same Source Data SQL Statement field?
>  
> Best,
> Gabi
>  
> <image001.jpg>
>  
>  
> Von: Tim Robertson [GBIF] [mailto:trobertson at gbif.org] 
> Gesendet: Mittwoch, 23. Oktober 2013 14:01
> An: Dröge, Gabriele
> Cc: ipt at lists.gbif.org
> Betreff: Re: [IPT] use of extensions; how can duplication of rows be avoided?
>  
> Hi Gabi,
>  
> In *typical* use there would be 1 SQL statement for the core, and then one SQL statement per extension.
> There are occasions that you would break this though.
>  
> If I were setting up an IPT on MySQL I would use views in the database, and manage those with the database database schema itself.  So something along the lines of:
>  
>   CREATE VIEW view_ipt_occurrence 
>   AS SELECT id AS id, id AS occurrenceID, name AS scientificName … FROM specimen; 
>   
>   CREATE VIEW view_ipt_image AS SELECT s.id AS id, s.id AS 
>   SELECT occurrenceID, i.image AS imageURL … FROM image i JOIN specimen s ON i.specimen_id=s.id; 
>  
> Then in the IPT on the occurrence mapping I would simply use this knowing it will auto map since the views use DwC terms as column aliases:
>   SELECT * FROM view_ipt_occurrence;
>   SELECT * FROM view_ipt_image;
>  
> Does that help at all?  
>  
> If you send your DB schema, we will be happy to help out with SQL mappings.
>  
> Thanks,
> Tim
>  
> On Oct 23, 2013, at 1:39 PM, Dröge, Gabriele wrote:
> 
> 
> Dear all,
>  
> I have a general question on Darwin Core and the use of Darwin Core extensions.
>  
> E.g. I want to use the Occurrence Core and Simple Images with a mysql database.
>  
> Problem: Only a few of my occurrences have images. The Darwin Core Archive creates a large images file with all occurrence IDs and only a few have also Image urls.
>  
> But I did expect a file with the image urls only (so much shorter) and all occurrences (with or without image) in the occurrences file.
>  
> The same problem appears for the identification extension the other way round (duplication of occurrence rows for multiple identifications) and every other extension I’ve tested…
>  
> But I am a bit confused how this can be done with only one big sql query (with some left joins). Do I have to use multiple resources to use multiple sql queries? Or is this a problem/bug of IPT?
>  
> Best,
> Gabi
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