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Asked: 2026-05-28T17:20:03+00:00

I am working on a project where I need to have data inherit at

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I am working on a project where I need to have data inherit at variable depths, and then be able to return any descendants of a particular piece of data. I am working with geographical regions, so I was thinking about having a “Region” table, and have everything from “North America” to individual neighborhoods such as “Bronx”. So, if someone types in “North America”, they should also receive results for “Bronx” because “Bronx” is a descendant of “North America” by means of the relationship
North America->United States->New York(State)->New York(City)->Bronx

In my DB I was planning on having the Region table link back to itself with a table that specifies a parent/child relationship between Regions. Here is an example of what I would propose:
enter image description here

Any help would be greatly appreciated!

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1 Answer

  1. Editorial Team

    Do you dont need a new table. A foreign key in major table is enough.

    This is my approach:

    First problem, design data schema: I keep hierarchis with a foreign key to parent row. It is simply. You have an example with hiererchy regions here:

    WOE_ID  ISO Name    Language    PlaceType   Parent_ID
20069843    "NA"    "Oshana"    ENG State   23424987
55921113    "NA"    "Ondangwa"  ENG County  20069843
...

    Second problem, retrieve ascendants/descendants: As you explain, problems comes with select: select some region and all descendants os ascendants. To solve this you should to create a new tree table. This table contains pairs: al combination to a person with all they ancestors (and itself):

    region( id, name, id_parent)
region_tree( id, id_ancestor, distance )

    Noticie that with this structure is easy to query hierarchies. Sample: all descendants of some region:

    select region.*, distance
from 
  region p
    inner join 
  region_tree t 
    on ( p.id = t.id)
where
  id_ancesor = **someregion.id **

    You can play with distance to get only sub-regions, sub-sub-regions, …

    Last problem, keep tree: tree must be all time up to data. You should automatize this: a trigger over region or a store procedure for CRUD operations,

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