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Re: join/relate tables with CQL - advise needed
by Jody Garnett-3
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So the quick answer is that the CQL syntax does not support the
concept of "AS" - it is limited to just the concept of WHERE.
The long answer is that the ReShape operation can process one feature
collection; and evaluate expressions to build up a new feature
collection. For the AuScope remapping work we have made a function
allow them to look up a value in a property file; and they also have
the idea of "feature chaining" where they make an expression that at
the end of the day will function as a join.
There work does exist now; I just have not had a chance to use it in
uDig. I will try and hunt down some docs for you and report back. This
work would be available for uDig 1.2.x as long as we add another
couple of jars into the mix.
Cheers,
Jody
On 23/10/2009, at 1:56 AM, hannes wrote:
> Dear uDIG developers,
>
> I have a question for you which eventually results in a request for
> uDIG
> enhancement..
>
> Situation:
> uDIG connected to PostgisDB
> 1) point file loaded
> 2) another table loaded, both contain a common used id (table is
> 300MB),
> this tables also contains a date column
>
> QUESTION:
> 3) how do i write a CQL statement to join a) both tables and b) select
> only one specific date.
>
>> From the manual I understand that I should use a FILTER for where
> functions and a Expression for a select function..
> In postgis(aaaehhh in SQL) I would write something like (for a table
> or
> view)
>
> CREATE table myschema.V2007 AS
> select myschema.station3.*,msmntval from
> myschema.station3, myschema.sample_00007_day
> WHERE
> myschema.station3.eucode = myschema.sample_00007_day.eucode
> AND extract (YEAR from myschema.sample_00007_day.sampledate) = 2007
> AND extract (MONTH from myschema.sample_00007_day.sampledate) = 3
> AND myschema.sample_00007_day.timestep = 3 ;
>
> but in uDIG now ?
>
>
> I was searching through the manuals, the email archives etc, but I'm
> somehow clueless how to perform that join/relate.
> Could anyone be so kind to share thoughts or codes to start with ?
> Coming from an researchers perspective, this function would be quite a
> needed feature.
>
> hannes
>
> PS.: I believe that I'm probably not the first to ask that question.
>
>
> _______________________________________________
> User-friendly Desktop Internet GIS (uDig)
> http://udig.refractions.net
> http://lists.refractions.net/mailman/listinfo/udig-devel
_______________________________________________
User-friendly Desktop Internet GIS (uDig)
http://udig.refractions.net
http://lists.refractions.net/mailman/listinfo/udig-devel
concept of "AS" - it is limited to just the concept of WHERE.
The long answer is that the ReShape operation can process one feature
collection; and evaluate expressions to build up a new feature
collection. For the AuScope remapping work we have made a function
allow them to look up a value in a property file; and they also have
the idea of "feature chaining" where they make an expression that at
the end of the day will function as a join.
There work does exist now; I just have not had a chance to use it in
uDig. I will try and hunt down some docs for you and report back. This
work would be available for uDig 1.2.x as long as we add another
couple of jars into the mix.
Cheers,
Jody
On 23/10/2009, at 1:56 AM, hannes wrote:
> Dear uDIG developers,
>
> I have a question for you which eventually results in a request for
> uDIG
> enhancement..
>
> Situation:
> uDIG connected to PostgisDB
> 1) point file loaded
> 2) another table loaded, both contain a common used id (table is
> 300MB),
> this tables also contains a date column
>
> QUESTION:
> 3) how do i write a CQL statement to join a) both tables and b) select
> only one specific date.
>
>> From the manual I understand that I should use a FILTER for where
> functions and a Expression for a select function..
> In postgis(aaaehhh in SQL) I would write something like (for a table
> or
> view)
>
> CREATE table myschema.V2007 AS
> select myschema.station3.*,msmntval from
> myschema.station3, myschema.sample_00007_day
> WHERE
> myschema.station3.eucode = myschema.sample_00007_day.eucode
> AND extract (YEAR from myschema.sample_00007_day.sampledate) = 2007
> AND extract (MONTH from myschema.sample_00007_day.sampledate) = 3
> AND myschema.sample_00007_day.timestep = 3 ;
>
> but in uDIG now ?
>
>
> I was searching through the manuals, the email archives etc, but I'm
> somehow clueless how to perform that join/relate.
> Could anyone be so kind to share thoughts or codes to start with ?
> Coming from an researchers perspective, this function would be quite a
> needed feature.
>
> hannes
>
> PS.: I believe that I'm probably not the first to ask that question.
>
>
> _______________________________________________
> User-friendly Desktop Internet GIS (uDig)
> http://udig.refractions.net
> http://lists.refractions.net/mailman/listinfo/udig-devel
_______________________________________________
User-friendly Desktop Internet GIS (uDig)
http://udig.refractions.net
http://lists.refractions.net/mailman/listinfo/udig-devel
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