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Asked: 2026-06-09T23:02:01+00:00

I have a very basic one table scenario; tblFamiles entryID : Int name: Text

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I have a very basic one table scenario;

tblFamiles
entryID : Int
name: Text
parentID: Int

Lets add the following rows;

entryID : name                  : parentID
1       : Grandmother Jones     : 0
2       : Grandmother Thompson  : 0
3       : Mother Jones          : 1
4       : Mother Thompson       : 2
5       : 1st Daughter Jones    : 3
6       : 2nd Daughter Jones    : 3
7       : 1st Daughter Thompson : 4

Here we have three generations of two familes stored, the Jones family and the Thompson family (as an exampe). I would like to query this table but order the results by the parentID (but not just like plain old ORDER BY 'parentID' DESC, so that they are in relative order. I would like an output like this;

SELECT (SOME MAGIC) FROM `tblFamiles`;
entryID : name                  : parentID
1       : Grandmother Jones     : 0
3       : Mother Jones          : 1
5       : 1st Daughter Jones    : 3
6       : 2nd Daughter Jones    : 3
2       : Grandmother Thompson  : 0
4       : Mother Thompson       : 2
7       : 1st Daughter Thompson : 4

Logically, the only way I can see how to do this is to loop through all entryIDs and then for each entryID; loop through all other records checking their parentID fields against the current entryID, and bringing those records to the top of the result set, under the current row. But I can’t see how to do that in MySQL.

UPDATE

I have used families as an example above, but what I am after is a method of storing nested entries and getting them in a single query, for efficiency really. I could just make multiple SELECT queries but that would be it ugly;

(Pseudo)
SELECT entryID, name WHERE parentID = 0 LIMIT 0,1;
print name;
 Sub query:
 SELECT entryID, name WHERE parentID = $above-entryID
 print name;
  (Keep looping through this till the second query returns no results, 
  then go back to the first query and move onto the next entryID)

2nd UPDATE

You can forget the name column even exists, I just used that as an example, all that matters here is entryID and parentID as these are the two columns that link and control everything. There could be twenty extra columns as well as name, but they all revolve around entryID and parentID, it’s just linked or nested (which term ever is more appropriate) IDs.

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1 Answer

  1. Editorial Team

    “But I can’t see how to do that in MySQL.”

    Short answer

    You can’t.

    Slight longer answer.

    The problem you’re trying to solve is not one that a relational database is a good solution for solving. What you’re trying to do would require a Object-relational database.

    For the theory I’d suggest reading the difference between the two:

    http://en.wikipedia.org/wiki/Relational_database

    http://en.wikipedia.org/wiki/Object-relational_database

    As well as questions on stackoverflow about why each are good/bad.

    https://stackoverflow.com/questions/800/object-oriented-vs-relational-databases or
    Object-oriented-like structures in relational databases

    Including this answer https://stackoverflow.com/a/600765/778719 which leads to
    The Vietnam of Computer Science.

    That is actually more about object mapping into a relational database, but it does show you the depth (and lack of obvious solutions) to the problem you’ve just encountered.

    The actual problem with using one when you actually need the other is called the Object-relational impedance mismatch
    http://en.wikipedia.org/wiki/Object-relational_impedance_mismatch

    Actually possibly useful answer

    The problem you described is one that is best handled by objects. I suggest just stick with storing them in a relational database for now, just accept the fact that your logic will need to live in the application code layer, not the SQL layer, and so make multiple queries to the database if you need to to fetch each ‘object’ or possibly each ‘layer’ of objects.

    That will work up until a point, at which point you will understand the problem better and be in a better position to either use a different technology, or at least understand the tradeoffs between different solutions.

    Horrifying bonus

    Cycles in family tree software

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