Question

I’ve got collection of geo objects in database:

There are four Tables:

Countries
Regions
Provinces
Cities

Cities has inter alia ProvinceCode
Provinces has inter alia regionCode
Regions has inter alia CountryCode

And there is fifth Table: Descriptions

ObjectCode
ObjectType(country, region, province, city)
Description.

How to get from Descriptions table, all descriptions from objects which are in the definite country ??

Answer 1

Putting away the soap box, here is an actual solution:

select Countries.code as  country_code  
       , count_d.description as country_desc
       , Regions.code as  region_code  
       , reg_d.description as region_desc
       , Provinces.code as  province_code  
       , prov_d.description as province_desc
       , Cities.code as  city_code  
       , city_d.description as city_desc
from  Countries
        join Descriptions count_d
             on ( count_d.ObjectCode  = Countries.code
                  and count_d.ObjectType = 'COUNTRY' )
        join Regions
             on ( Regions.CountryCode = Countries.code )
        join Descriptions reg_d
             on ( region_d.ObjectCode  = Regions.code
                  and count_d.ObjectType = 'REGION' )
        join Provinces
             on ( Provinces.RegionCode  = Regions.code )
        join Descriptions prov_d
             on ( prov_d.ObjectCode  = Provinces.code
                  and count_d.ObjectType = 'PROVINCE' )
        join Cities
             on ( Cities.ProvinceCode  = Provinces.code )
        join Descriptions city_d
             on ( city_d.ObjectCode  = Cities.code
                  and count_d.ObjectType = 'CITY' )
where Countries.whatever = 'DONDESTAHN'
/

Not actually tested, so watch out for typos! They’re a particular danger with Cut’N’Paste Driven Development.