List:General Discussion« Previous MessageNext Message »
From:Peter Brawley Date:May 24 2007 4:37pm
Subject:Re: expanding hierarchies
View as plain text  
Naz writes

 >The definitive answer to anything that
 >requires trees in SQL is nested sets.

They are not definitive when the tree is large and must be updated 
frequently.

PB

-----

Naz Gassiep wrote:
> The definitive answer to anything that requires trees in SQL is nested
> sets. I have written a tutorial on the subject, as this is about the
> most asked question in DB relational data modeling.
>
> http://www.mrnaz.com/static/articles/trees_in_sql_tutorial/
>
> Enjoy :)
>
> - Naz.
>
> Peter Brawley wrote:
>   
>> tbt
>>
>>     
>>> the number of levels in this table is unknown and the query should work
>>>  for any number of levels
>>>  please provide a sample 'select' query in mysql
>>>       
>> That's a graph, which is recursive, so you need an sproc. See edge
>> list sprocs at
>> http://www.artfulsoftware.com/mysqlbook/sampler/mysqled1ch20.html.
>>
>> PB
>>
>> -----
>>
>> tbt wrote:
>>     
>>>> Hi
>>>>
>>>> i have a table like this
>>>>
>>>> id      name        parent_id
>>>> 1       europe
>>>> 2       spain       1
>>>> 3       england     1
>>>> 4       france      1
>>>> 5       london      3
>>>> 6       mayfair     5
>>>> 7       madrid      2
>>>>
>>>> in this table each destination is mapped to a parent destination
>>>> eg: mayfair is mapped to london, london is mapped to england etc.
>>>>
>>>> i like to write a query to find child destinations when an id is
>>>> given for
>>>> a parent destination
>>>> eg: if 3 is the id, then the result of query should be 3,5,6
>>>> if 2 is the id, then the result should be 2,7
>>>>
>>>> the number of levels in this table is unknown and the query should work
>>>> for any number of levels
>>>> please provide a sample 'select' query in mysql
>>>>     
>>>>         
>
>   

Thread
expanding hierarchiestbt24 May
  • Re: expanding hierarchiesPeter Brawley24 May
    • Re: expanding hierarchiesNaz Gassiep24 May
      • Re: expanding hierarchiesPeter Brawley24 May
        • Re: expanding hierarchiesNaz Gassiep24 May
Re: expanding hierarchiesPeter Brawley24 May