Question

I’m new in this domain and like to write an application managing genealogical data. My main concern is how to store and retreive these data from MySQL. I know that DB like Oracle are optimised for recursive queries, but maybe I can find an alternative solution to use MySQL which I undestand is not supporting “CONNECT” .
PS. I know that there are thousands of existing Open source solutions, but consider that these data will be a limited part of the functionality, and I need to keep control of the full code.

I had a quick look on the web and found some interesting approach, for instance Interval-based algo which is perfect for queries but not satisfactory for update / deletion.

I’m going to have a look on Prefix-based(Dewey) approach, but one may know an efficient and proven approach to share ?

thanks

gilles

Answer 1

First problem, design data schema: I keep hierarchis with a foreign key to parent row. It is simply.

Second problem, retrieve ascendants/descendants: As you explain, problems comes with select: select some people 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):

people( id, name, id_parent)
people_tree( id, id_ancestor, distance )

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

select people.*, distance
from 
  people p
    inner join 
  people_tree t 
    on ( p.id = t.id)
where
  id_ancesor = **sombody.id **

You can play with distance to get only grandparents, grandwchildren, etc. …

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

EDITED

Because this is a Genealogy tree, each person must to have both references, parent and mother:

people( id, name, id_parent, id_mother)

Then, 2 trees are needed:

parent_ancestors_tree( id, id_ancestor, distance )
mother_ancestors_tree( id, id_ancestor, distance )

David ask for sample data:

people: id    name    id_parent    id_mother
         1    Adam         NULL      NULL
         2    Eva          NULL      NULL
         3    Cain            1         2
        ..    ...
         8    Enoc            3         5

parent_ancestors_tree id    id_ancestor  distance
              (Adam)   1              1         0
              (Eva)    2              2         0
              (Cain)   3              3         0
                       3              1         1
              (Enoc)   8              8         0
                       8              3         1
                       8              1         2

mother_ancestors_tree id    id_ancestor  distance
              (Adam)   1              1         0
              (Eva)    2              2         0
              (Cain)   3              3         0
                       3              2         1
              (Enoc)   8              8         0
                  -- here ancestors of Enoc's mother --

regards.