[postgis-users] Union of 7 datasets

Andreas Laggner andreas.laggner at fal.de
Tue Sep 25 06:41:02 PDT 2007


Hi Regina,

your last hint with collect brings me closer to my goal!!
I ran this query now - my geometries are exactly what i wanted to have! 
There only problem left is: If polygons intersect, they always have the 
attributes from spa only, never from ffh. Parts, that contain spa AND 
ffh only have the spa-attributes, and this parts from a overlapping 
polygon, that are only ffh, have no attributes at all.
Can you find the error in the query?

cheers      Andreas

drop table natura2000;
create table natura2000
    (ffh_name character varying(80),ffh_land character varying(3),ffh 
smallint,ffh_id smallint,
     spa_name character varying(80),spa_land character varying(3),spa 
smallint,spa_id smallint)
    with oids;
select 
addgeometrycolumn('','natura2000','the_geom','31467','MULTIPOLYGON',2);
alter table natura2000 drop constraint enforce_geotype_the_geom;

insert into natura2000 
(ffh_name,ffh_land,ffh,ffh_id,spa_name,spa_land,spa,spa_id,the_geom)
 select ffh_rep.ffh_name,ffh_rep.ffh_land,ffh_rep.ffh,ffh_rep.ffh_id,
    spa_rep.spa_name,spa_rep.spa_land,spa_rep.spa,spa_rep.spa_id,
    collect(ffh_rep.the_geom, spa_rep.the_geom) as geomcollection
    from ffh_rep inner join spa_rep
    on (ffh_rep.the_geom && spa_rep.the_geom and 
intersects(ffh_rep.the_geom, spa_rep.the_geom))
    union all
 -- the second select gives you ffh_reps that have no spa_reps - your 15
   select ffh_rep.ffh_name,ffh_rep.ffh_land,ffh_rep.ffh,ffh_rep.ffh_id,
      null as spa_name, null as spa_land, null as spa, null as spa_id,
      ffh_rep.the_geom as the_geom
   from ffh_rep left join spa_rep
    on (ffh_rep.the_geom && spa_rep.the_geom and 
intersects(ffh_rep.the_geom, spa_rep.the_geom))
    where spa_rep.the_geom is null
    union all
 -- and the 3rd gives you spa_reps that have no ffh_reps. - your 40
    select  null as ffh_name, null as ffh_land, null as ffh, null as ffh_id,
        spa_rep.spa_name,spa_rep.spa_land,spa_rep.spa,spa_rep.spa_id,
        spa_rep.the_geom AS the_geom
    from spa_rep left join ffh_rep
    on (ffh_rep.the_geom && spa_rep.the_geom and 
intersects(ffh_rep.the_geom, spa_rep.the_geom))
    where ffh_rep.the_geom is null;



Obe, Regina schrieb:
> Not sure I quite understand the question.  You mean to store these 3 geometries separately so you can color code as needed or overlay as needed?
>
> In that case you would have 3 separate geometry fields
>
>   intersection(ffh_rep.the_geom, spa_rep.the_geom) As geomintersection, ffh_rep.the_geom As ffh_geom, spa_rep.the_geom As spa_geom
>
> For the ones where there is only udo or kai then I guess you can fill in the same geometry for all geometry fields.
>
>
> and then overlay them on your map as separate layers as needed
>
> or if you mean you just want it to look like figure 1 but not necessarily color coded, then you would do
>
> collect(ffh_rep.the_geom, spa_rep.the_geom) as geomcollection
>
> Hope that helps,
> Regina
>
>
>
> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Andreas Laggner
> Sent: Thursday, August 30, 2007 7:24 AM
> To: PostGIS Users Discussion
> Subject: Re: [postgis-users] Union of 7 datasets
>
> Moin Regina,
>
> the query you suggested is a very big step forward, but it does not 
> exactly what i want to have  ;-)  ...  it seems to me i will need an 
> intersection in one part and not a geomunion!! But i want to ask you:
> what it does correctly: I now have a union of all geometries from both 
> source datasets.
> If i have a single udo (ffh_rep) that intersects no kai (spa_rep) the 
> row only has the attributes from udo. Same thing i have with single kai. 
> That is all correct.
> BUT: If udo and kai intersects i will not have new polygons!! For 
> example: blue is udo (or ffh_rep) and yellow is kai (or spa_rep). I want 
> to have three polygons than with blue only the attributes from udo, 
> yellow only the attributes from kai AND the intersection, polygon number 
> 3, the green one (blue with yellow points) with the attributes from udo 
> and kai (figure1). And now i have one Polygon having the attributes from 
> udo and kai (figure2).
>
> figure1:
> figure1
>
> figure2:
>
> figure2
>
>
> My query:
> drop table natura2000;
> create table natura2000
>     (ffh_name character varying(80),ffh_land character varying(3),ffh 
> smallint,ffh_id smallint,
>      spa_name character varying(80),spa_land character varying(3),spa 
> smallint,spa_id smallint)
>     with oids;
> select 
> addgeometrycolumn('','natura2000','newgeom','31467','MULTIPOLYGON',2);
> alter table natura2000 drop constraint enforce_geotype_newgeom;
>
> insert into natura2000 
> (ffh_name,ffh_land,ffh,ffh_id,spa_name,spa_land,spa,spa_id,newgeom)
>  select ffh_rep.ffh_name,ffh_rep.ffh_land,ffh_rep.ffh,ffh_rep.ffh_id,
>     spa_rep.spa_name,spa_rep.spa_land,spa_rep.spa,spa_rep.spa_id,
>     geomunion(ffh_rep.the_geom, spa_rep.the_geom) as newgeom
>   from ffh_rep inner join spa_rep
>     on (ffh_rep.the_geom && spa_rep.the_geom and 
> intersects(ffh_rep.the_geom, spa_rep.the_geom))
>     union all
>  -- the second select gives you ffh_reps that have no spa_reps - your 15
>    select ffh_rep.ffh_name,ffh_rep.ffh_land,ffh_rep.ffh,ffh_rep.ffh_id,
>       null as spa_name, null as spa_land, null as spa, null as spa_id,
>       ffh_rep.the_geom as newgeom
>    from ffh_rep left join spa_rep
>     on (ffh_rep.the_geom && spa_rep.the_geom and 
> intersects(ffh_rep.the_geom, spa_rep.the_geom))
>     where spa_rep.the_geom is null
>     union all
>  -- and the 3rd gives you spa_reps that have no ffh_reps. - your 40
>     select  null as ffh_name, null as ffh_land, null as ffh, null as ffh_id,
>         spa_rep.spa_name,spa_rep.spa_land,spa_rep.spa,spa_rep.spa_id,
>         spa_rep.the_geom AS newgeom
>     from spa_rep left join ffh_rep
>     on (ffh_rep.the_geom && spa_rep.the_geom and 
> intersects(ffh_rep.the_geom, spa_rep.the_geom))
>     where ffh_rep.the_geom is null;
>
> Cheers    Andreas
>
>
>
> Obe, Regina schrieb:
>   
>> Andreas,
>>
>> You would use the SQL UNION predicate like shown below (actually 
>> slight correction - it is speedier to use UNION ALL especially when 
>> you know there will not be dupiclates since it saves the processing of 
>> sorting to get a distinct UNION does an implicit distinct)  - so I 
>> have corrected below.
>>
>> -  - I happened to insert comments in between which may have confused 
>> you, but you should be able to run the whole thing as one statement or 
>> if you prefer because of speed issues run each insert separately.
>>
>> So  would be
>> INSERT INTO sometable(field1, field2,field3,field4, newgeom)
>>  SELECT udo.field1, udo.field2, kai.field3, kai.field4, 
>> geomunion(udo.the_geom, kai.the_geom) AS newgeom
>>   FROM udo INNER JOIN kai ON (udo.the_geom && kai.the_geom AND 
>> intersects(udo.the_geom, kai.the_geom))
>>   UNION ALL
>>  -- the second select gives you udos that have no kais - your 15
>>   SELECT udo.field1, udo.field2, NULL As field3, NULL As field4, 
>> udo.the_geom AS newgeom
>>   FROM udo LEFT JOIN kai ON (udo.the_geom && kai.the_geom AND 
>> intersects(udo.the_geom, kai.the_geom))
>>   WHERE kai.the_geom IS NULL
>>  UNION ALL
>>  -- and the 3rd gives you kais that have no udos. - your 40
>>   SELECT NULL As field1, null As field2, kai.field3, kai.field4, 
>> kai.the_geom AS newgeom
>>   FROM kai LEFT JOIN udo ON (udo.the_geom && kai.the_geom AND 
>> intersects(udo.the_geom, kai.the_geom))
>>   WHERE udo.the_geom IS NULL;
>>
>>  
>>
>> ----If FULL JOIN were to work (which in theory it should, but doesn't 
>> seem to with Postgis functions  (HINT HINT: would be nice if 
>> that worked and can be easily fixed (but sadly I think the issue is 
>> deeper than Postgis and Geos) - you could write the above much simpler as)
>>
>> INSERT INTO sometable(field1, field2,field3,field4, newgeom)
>>  SELECT udo.field1, udo.field2, kai.field3, kai.field4, 
>> COALESCE(geomunion(udo.the_geom, kai.the_geom), udo.the_geom, 
>> kai.the_geom) AS newgeom
>>   FROM udo FULL JOIN kai ON (udo.the_geom && kai.the_geom AND 
>> intersects(udo.the_geom, kai.the_geom))
>>
>> Now if you have a lot of these and the tables are very similar in 
>> nature and named in a predictable way then the way I usually handle it 
>> is to write a pgsql function that dynamically generates the SQL 
>> statement to execute either via a FOR loop and then executes the built 
>> SQL or set of SQL statements or you could do a similar thing in some 
>> scripted language like perl or php.
>>
>> I take it SQL and pgsql and all that is fairly new to you so it might 
>> be worthwhile (even though its a lot of typing) to do it the long cut 
>> and paste way if nothing more than an exercise to get a feel of how 
>> this all works and visualize the patterns at play.
>>
>> I don't get the sense that I comprehend your full problem.   
>> Unfortunately I don't have any experience with ArcGIS/ArcView ways of 
>> doing things, so I'm not quite sure if there is an equivalent way in 
>> PostGIS/PostgreSQL  world of doing the same kind of thing and what 
>> exactly that thing is you are doing in ArcGIS.
>>
>> Union has 3 meanings in PostGIS/PostgreSQL (actually stuff your 
>> favorite spatial/DB here - all non-trivial spatial relational dbs 
>> behave more or less the same)  
>>
>> 1) unioning of record sets (standard ANSI SQL UNION/UNION ALL) - which 
>> is simply a way of stringing together a bunch of selects into a 
>> single result set as shown above
>>
>> 2)  unioning of 2 geometry fields like shown above with geomunion
>>
>> 3) Aggregate  geomunion - aggregate variant of the above geomunion 
>> function that groups and unions a whole setof geometries together but 
>> requires you are grouping by some field or set of fields).
>>
>> I must also mention there is collect (non-aggregate and aggregate 
>> function) which often times is just as effective as the geomunion and 
>> in general much faster processor wise.
>>
>> Hope that helps,
>>
>> Regina
>>
>> -----Original Message-----
>> From: postgis-users-bounces at postgis.refractions.net 
>> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of 
>> Andreas Laggner
>> Sent: Tuesday, August 28, 2007 9:13 AM
>> To: PostGIS Users Discussion
>> Subject: Re: [postgis-users] Union of 7 datasets
>>
>> Obe, Regina schrieb:
>>     
>>>  Sounds like you would have to go with a full join type thing with 
>>>       
>> workaround I described below (last example).  So If I understand you 
>> correctly then something like this - 
>>     
>>> --the first select gives you those records in both tables your 25 udokai
>>>  SELECT udo.field1, udo.field2, kai.field3, kai.field4, 
>>>       
>> geomunion(udo.the_geom, kai.the_geom) AS newgeom
>>     
>>>  FROM udo INNER JOIN kai ON (udo.the_geom && kai.the_geom AND 
>>>       
>> intersects(udo.the_geom, kai.the_geom))
>>     
>>>  UNION
>>> -- the second select gives you udos that have no kais - your 15
>>>  SELECT udo.field1, udo.field2, NULL As field3, NULL As field4, 
>>>       
>> udo.the_geom AS newgeom
>>     
>>>  FROM udo LEFT JOIN kai ON (udo.the_geom && kai.the_geom AND 
>>>       
>> intersects(udo.the_geom, kai.the_geom))
>>     
>>>  WHERE kai.the_geom IS NULL
>>>  UNION
>>> -- and the 3rd gives you kais that have no udos. - your 40
>>>  SELECT nul As field1, null As field2, kai.field3, kai.field4, 
>>>       
>> kai.the_geom AS newgeom
>>     
>>>  FROM kai LEFT JOIN udo ON (udo.the_geom && kai.the_geom AND 
>>>       
>> intersects(udo.the_geom, kai.the_geom))
>>     
>>>  WHERE udo.the_geom IS NULL
>>>
>>> Unioned together you should get
>>> 25 + 15 + 40 = ? 80
>>>
>>> Hope that helps,
>>> Regina
>>>
>>>  
>>>       
>> UFF - that seems to be a complex question, a comprehensive operation and
>> a lot to type too!!! Thanks a million - i would have spent many time to
>> find out this query by myself! Ok..... how can i perform your "UNION": I
>> would just insert my selects one after another in one new table - will
>> that work well?
>> I want to aggregate around 20 datasets this way!? Do you know a method
>> to operate with more datasets (for example 7) in a effektiv manner and
>> not to do this three selects 6 times?
>> AND: Am i totally wrong with my aims? It seems to me that is an exotic
>> think to do with PostGis, but our projects/problems require to aggregate
>> datasets in almost all cases (around 90%) and that is exactly what one
>> of the basic functions "Union" in ArcView already carried out ten years
>> ago. So i would exspect there is a function to perform this operation
>> easier!? .....i just wonder.....
>>
>>
>> cheers      Andreas
>>
>>     
>>> -----Original Message-----
>>> From: postgis-users-bounces at postgis.refractions.net 
>>>       
>> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of 
>> Andreas Laggner
>>     
>>> Sent: Tuesday, August 28, 2007 7:28 AM
>>> To: PostGIS Users Discussion
>>> Subject: Re: [postgis-users] Union of 7 datasets
>>>
>>> Obe, Regina schrieb:
>>>  
>>>       
>>>> BASIC TRICK:  If you want to get all records with no matching 
>>>>         
>> including those that match - put what you would normally put in your 
>> WHERE clause in the JOIN clause and use a LEFT JOIN.
>>     
>>>>    
>>>>         
>>> ok - it seems to me i need some coaching......Yes, I want to get all
>>> records with no matching including those that match, but i also want to
>>> dissect the polygons that matches. I will try to explain again just to
>>> be sure you understood my aims: I have 20 polygons in udo and 50 in kai.
>>> 10 from kai are intersecting 5 from udo to 25 new polygons i call udokai
>>> (because they have attributes from udo AND kai). My result should have:
>>> 15 polygons with attributes only from udo, 40 polygons with attributes
>>> only from kai AND 25 with attributes from udo and kai! In most cases i
>>> want to do such a operation because i want to aggregate (spatial
>>> correct) different datasets!
>>> Which example from you fits best for this aim? I did not find any
>>> information on how left join works on the postgis or postgresql 
>>>       
>> reference...
>>     
>>>  
>>>       
>>>> Unfortunately as I have come across before if you need an either or 
>>>>         
>> (if in table 1 or table 2 - ideally you would use a FULL JOIN but for 
>> some reason Postgres chokes when you use postgis functions in the FULL 
>> JOIN clause for the cases I have tried).  In that case you need a 
>> workaround using a set of UNIONS.
>>     
>> --------------------------------------------------------------------------
>>     
>>>> Simplest case - get all records in g1 one or union of g1 and g2 
>>>>         
>> that intersect
>>     
>>>> NOTE: COALESCE is an ANSI SQL function that will return the first 
>>>>         
>> non-null - when you do a geomunion of a geometry and null you get null 
>> which is why we need COALESCE
>>     
>>>> SELECT g1.field1, g1.field2, COALESCE(geomunion(g1.the_geom, 
>>>>         
>> g2.the_geom), g1.the_geom) AS newgeom
>>     
>>>> FROM g1 LEFT JOIN g2 ON (g1.the_geom && g2.the_geom AND 
>>>>         
>> intersects(g1.the_geom, g2.the_geom))
>>     
>>>>         
>> -----------------------------------------------------------------------------------------
>>     
>>>> Either of case - get all geometries in g1 or g2 or union if there 
>>>>         
>> is a match - workaround for full joins not working right
>>     
>>>> SELECT g1.field1, g1.field2, geomunion(g1.the_geom, g2.the_geom) AS 
>>>>         
>> newgeom
>>     
>>>> FROM g1 INNER JOIN g2 ON (g1.the_geom && g2.the_geom AND 
>>>>         
>> intersects(g1.the_geom, g2.the_geom))
>>     
>>>> UNION
>>>> SELECT g1.field1, g1.field2, g1.the_geom AS newgeom
>>>> FROM g1 LEFT JOIN g2 ON (g1.the_geom && g2.the_geom AND 
>>>>         
>> intersects(g1.the_geom, g2.the_geom))
>>     
>>>> WHERE g2.the_geom IS NULL
>>>> UNION
>>>> SELECT g1.field1, g1.field2, g2.the_geom AS newgeom
>>>> FROM g2 LEFT JOIN g1 ON (g1.the_geom && g2.the_geom AND 
>>>>         
>> intersects(g1.the_geom, g2.the_geom))
>>     
>>>> WHERE g1.the_geom IS NULL
>>>>
>>>>
>>>>
>>>> Hope that helps,
>>>> Regina
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: postgis-users-bounces at postgis.refractions.net 
>>>>         
>> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of 
>> Andreas Laggner
>>     
>>>> Sent: Thursday, August 23, 2007 11:32 AM
>>>> To: PostGIS Users Discussion
>>>> Subject: Re: [postgis-users] Union of 7 datasets
>>>>
>>>> Obe, Regina schrieb:
>>>>  
>>>>    
>>>>         
>>>>> Oh the g1 g2 .. was just for example - I don't actually call my 
>>>>>           
>> tables meaningless names like that. 
>>     
>>>>> You should be doing a join on something or have a where clause 
>>>>>           
>> unless one of your tables has only one record.  Otherwise you are 
>> doing what is called a CROSS JOIN (cartesian product)  which gives you 
>> an nxm records where n is the number of records in your first table 
>> and m is the number in second table.  This is generally a big NO NO.  
>> In certain rare cases you do want to do something like that, but is 
>> usually the exception.
>>     
>>>>>  
>>>>>    
>>>>>      
>>>>>           
>>>> I think the records in my targed table must be added (more or less) and
>>>> not multiplied! My Aim is a table that contains the areas of all the 7
>>>> sourcetables and the information which refuges are inside and wich not.
>>>> Perhaps i must use the intersection!? If i do my query with a gist like
>>>> this: where t1.the_geom && t2.the_geom; than the operation is very fast
>>>> (about one minute) but i only have the Polygons covered by BOTH
>>>> datasets, and i want to have as well those, which are covered by one
>>>> dataset only!! But my operation without the where clause runs for 4
>>>> hours now - that shows me there is something wrong  ;-)
>>>>  
>>>>    
>>>>         
>>>>> Its hard for me to tell if you need a cartesian product in this 
>>>>>           
>> case since I'm not quite sure what for example nature and biosphere 
>> represent.  I would guess that is wrong and you should first figure 
>> out which sets of say nature records you need to geomunion with 
>> biosphere and then join by that field or set of fields.
>>     
>>>>> It would help a bit if you could provide some sample questions you 
>>>>>           
>> expect to answer with your statistical analysis.  My guess is you may 
>> be better off with more than one table.
>>     
>>>>>  
>>>>>    
>>>>>      
>>>>>           
>>>> Sample question: give me all areas (all polygons) from germany where
>>>> landuse=arable land and soils=good and precipitation>600 and any (of 7)
>>>> reserves and so on.......
>>>> I need the values in my table to calculate the potential yield or other
>>>> things...
>>>> And i want to analyse such questions with a statistical software (SAS),
>>>> so it seems to me i need one table to import in SAS (or to query from
>>>> SAS directly to the postgresql).
>>>>
>>>> Thanks for your help, i will be back in my office in 
>>>>         
>> Monday.......Andreas
>>     
>>>>  
>>>>    
>>>>         
>>>>> Which structure is best really boils down to what questions you 
>>>>>           
>> hope to answer because one approach may make one question easy and 
>> fast and another question slow and cumbersome.
>>     
>>>>> Hope that helps,
>>>>> Regina
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> -----Original Message-----
>>>>> From: postgis-users-bounces at postgis.refractions.net 
>>>>>           
>> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of 
>> Andreas Laggner
>>     
>>>>> Sent: Thursday, August 23, 2007 10:04 AM
>>>>> To: PostGIS Users Discussion
>>>>> Subject: Re: [postgis-users] Union of 7 datasets
>>>>>
>>>>> Obe, Regina schrieb:
>>>>>  
>>>>>    
>>>>>      
>>>>>           
>>>>>> Andreas,
>>>>>>
>>>>>> It would help to know what your table structure looks like and 
>>>>>>             
>> why do you want to put them all in a single geometry?
>>     
>>>>>>  
>>>>>>    
>>>>>>      
>>>>>>        
>>>>>>             
>>>>> My table structures are a little bit different. I want to have 
>>>>>           
>> them in a
>>     
>>>>> single geometry to intersect them with other data and built a large
>>>>> table to run statistics over it (production site analysis over 
>>>>>           
>> germany).
>>     
>>>>>  
>>>>>    
>>>>>      
>>>>>           
>>>>>> I'm imaging you are you doing something like
>>>>>>
>>>>>> SELECT g1.somefield, geomunion(geomunion(g1.the_geom, 
>>>>>>             
>> g2.the_geom), g3.the_geom)
>>     
>>>>>> FROM g1 INNER JOIN g2 on g1.somefield = g2.somefield INNER JOIN 
>>>>>>             
>> g3 on g2.somefield = g3.somefield
>>     
>>>>>> GROUP BY g1.somefield
>>>>>>
>>>>>>  
>>>>>>    
>>>>>>      
>>>>>>        
>>>>>>             
>>>>> That´s an interesting method with inner join..why go you call your
>>>>> tables g1. g2. and so on?
>>>>> That´s my method i am using right now (geomunion 1 to 3 from 6), seems
>>>>> to be a pedestrian method :-(
>>>>>
>>>>> create table natura2000
>>>>>     (ffh_name character varying(80), ffh_land character 
>>>>>           
>> varying(3), ffh
>>     
>>>>> smallint, ffh_id smallint,
>>>>>      spa_name character varying(80), spa_land character 
>>>>>           
>> varying(3), spa
>>     
>>>>> smallint, spa_id smallint) with oids;
>>>>> select
>>>>>
>>>>>           
>> addgeometrycolumn('','natura2000','the_geom','31467','MULTIPOLYGON',2);
>>     
>>>>> alter table natura2000 drop constraint enforce_geotype_the_geom;
>>>>> insert into natura2000
>>>>>     select
>>>>>
>>>>>           
>> t1.ffh_name,t1.ffh_land,t1.ffh,t1.ffh_id,t2.spa_name,t2.spa_land,t2.spa,t2.spa_id,
>>     
>>>>>             geomunion(t1.the_geom, t2.the_geom)
>>>>>             from ffh_rep t1, spa_rep t2;
>>>>>
>>>>> create table sg71
>>>>>     (ffh_name character varying(80), ffh_land character 
>>>>>           
>> varying(3), ffh
>>     
>>>>> smallint, ffh_id smallint,
>>>>>      spa_name character varying(80), spa_land character 
>>>>>           
>> varying(3), spa
>>     
>>>>> smallint, spa_id smallint,
>>>>>      bio_name character varying(70), bio smallint, bio_id 
>>>>>           
>> smallint) with
>>     
>>>>> oids;
>>>>> select 
>>>>>           
>> addgeometrycolumn('','sg71','the_geom','31467','MULTIPOLYGON',2);
>>     
>>>>> alter table sg71 drop constraint enforce_geotype_the_geom;
>>>>> insert into sg71
>>>>>     select t1.ffh_name, t1.ffh_land, t1.ffh, t1.ffh_id, t1.spa_name,
>>>>> t1.spa_land, t1.spa, t1.spa_id,
>>>>>             t2.name,t2.bio,t2.bio_id,geomunion(t1.the_geom, 
>>>>>           
>> t2.the_geom)
>>     
>>>>>             from natura2000 t1, biosphere t2;
>>>>>
>>>>> create table sg72
>>>>>        (ffh_name character varying(80), ffh_land character varying(3),
>>>>> ffh smallint, ffh_id smallint,
>>>>>     spa_name character varying(80), spa_land character varying(3), spa
>>>>> smallint, spa_id smallint,
>>>>>     bio_name character varying(70), bio smallint, bio_id smallint,
>>>>>     np_name character varying(60), np smallint, np_id smallint) 
>>>>>           
>> with oids;
>>     
>>>>> select 
>>>>>           
>> addgeometrycolumn('','sg72','the_geom','31467','MULTIPOLYGON',2);
>>     
>>>>> alter table sg72 drop constraint enforce_geotype_the_geom;
>>>>> insert into sg72
>>>>>     select t1.ffh_name, t1.ffh_land, t1.ffh, t1.ffh_id, t1.spa_name,
>>>>> t1.spa_land, t1.spa, t1.spa_id,
>>>>>             t1.bio_name,t1.bio,t1.bio_id,t2.np_name,t2.np,t2.np_id,
>>>>>             geomunion(t1.the_geom, t2.the_geom)
>>>>>             from sg71 t1, np t2;
>>>>> AND SO ON......
>>>>>  
>>>>>    
>>>>>      
>>>>>           
>>>>>> or
>>>>>>
>>>>>> SELECT g1.somefield, geomunion(gt.the_geom)
>>>>>> FROM (SELECT somefield, the_geom FROM g1 UNION SELECT somefield, 
>>>>>>             
>> the_geom FROM g2 ...) gt
>>     
>>>>>> GROUP BY gt.somefield
>>>>>>
>>>>>>
>>>>>> If I have 7 different tables that have pretty much the same 
>>>>>>             
>> structure, but for logistical or other technical reasons (such as each 
>> has additional attributes distinct from one another), I need to keep 
>> them as separate tables, then I usually use inherited tables for that. 
>> That way when I need to join all datasets at once, I can simply query 
>> the parent table and it will automatically drill down to the child 
>> tables. Not sure if that helps more than it confuses your situation.
>>     
>>>>>> Then instead of the above I can simply do
>>>>>>
>>>>>> SELEG myparenttable.somefield, geomunion(myparenttable.the_geom)
>>>>>> FROM myparenttable
>>>>>> GROUP by gh.somefield
>>>>>>
>>>>>>
>>>>>>  
>>>>>>    
>>>>>>      
>>>>>>        
>>>>>>             
>>>>> ok - i have to think about your suggestions......that´s my second week
>>>>> with postgis.
>>>>> Can you tell me from my SQL-Statements which method will be best? So i
>>>>> try to understand that one.....
>>>>>
>>>>> Thanks for your reply!!!
>>>>>  
>>>>>    
>>>>>      
>>>>>           
>>>>>> Hope that helps,
>>>>>> Regina
>>>>>>
>>>>>> -----Original Message-----
>>>>>> From: postgis-users-bounces at postgis.refractions.net 
>>>>>>             
>> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of 
>> Andreas Laggner
>>     
>>>>>> Sent: Thursday, August 23, 2007 9:11 AM
>>>>>> To: PostGis_Mailinglist
>>>>>> Subject: [postgis-users] Union of 7 datasets
>>>>>>
>>>>>> Hi users,
>>>>>>
>>>>>> i want to put together 7 datasets to have all the different 
>>>>>>             
>> refuges in
>>     
>>>>>> one table (and in one geometry). Am i doing right with 6 times 
>>>>>>             
>> geomunion
>>     
>>>>>> (that´s much to type with all the attributes) or is there a more
>>>>>> effective way?
>>>>>>
>>>>>> cheers Andreas
>>>>>>
>>>>>>  
>>>>>>    
>>>>>>      
>>>>>>        
>>>>>>             
>>>>>  
>>>>>    
>>>>>      
>>>>>           
>>>>  
>>>>    
>>>>         
>>>  
>>>       
>> --
>> Dipl. Geoökologe Andreas Laggner
>> Institut für Ländliche Räume (LR)
>> Bundesforschungsanstalt für Landwirtschaft (FAL)
>>
>> Institute of Rural Studies
>> Federal Agricultural Research Centre (FAL)
>>
>> Bundesallee 50
>> D-38116 Braunschweig
>>
>> Tel.: (+49) (0)531 596 5515
>> Fax: (+49) (0)531 596 5599
>> E-mail: andreas.laggner at fal.de
>> Homepage: http://www.lr.fal.de/
>>
>> _______________________________________________
>> postgis-users mailing list
>> postgis-users at postgis.refractions.net
>> http://postgis.refractions.net/mailman/listinfo/postgis-users
>>
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>   


-- 
Dipl. Geoökologe Andreas Laggner
Institut für Ländliche Räume (LR)
Bundesforschungsanstalt für Landwirtschaft (FAL)

Institute of Rural Studies
Federal Agricultural Research Centre (FAL)

Bundesallee 50
D-38116 Braunschweig

Tel.: (+49) (0)531 596 5515
Fax: (+49) (0)531 596 5599
E-mail: andreas.laggner at fal.de
Homepage: http://www.lr.fal.de/ 




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