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List:       php-general
Subject:    Re: [PHP] Recursion with database tables
From:       Jono Bacon <jonobacon_lists () yahoo ! co ! uk>
Date:       2003-02-19 12:55:23
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Ernest E Vogelsinger wrote:

>At 14:43 19.02.2003, Jono Bacon said:
>--------------------[snip]--------------------
>  
>
>>At the moment I have three tables: Topic, Message, Comment. A topic has 
>>messages and each message can have comments. I have set this up with a 
>>table each and a field for the id of the parent (e.g. a comment will 
>>have the id of the message that it refers to).
>>
>>My mate said to me that I should really put all of this in one big table 
>>with a parent and child field. He said that my code should then figure 
>>out what is the child of what and how it is displayed.
>>    
>>
>
>This are one-to-many relationships? If yes, then your mate is wrong, you
>can't easily implement one-to-many using a single table.
>  
>
<snip>


Hi Ernest,

Thanks for your swift response.

The code that you posed is the technique I have used at the moment. This 
technique works fine, but like my mate said, this limits me to a single 
parent for a comment/message. I admit that is unlikely that I would need 
more than one parent, but what would happen if I changed the parent - 
would this model still work fine?

I am considering sticking with this technique - it seems to make more 
sense and I thought it would be quicker for queries as I wouldnt have to 
query a single table with a million rows.

One questions though - if I delete a topic, I need to delete all of its 
child messages and all of the child comments from each message. What is 
the best technique to do this? This has been driving me up the wall as 
it seems to involve some kind of looping and recursion.

    Jono




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