[Typo3-dev] database relations in TYPO3

[Ries van Twisk]

JoH wrote:

>>>>>You cannot put multiple relations in int field. So, blog is for
>>>>>multiple relations (though I would prefer text). And I think blog
>>>>>is used in case of single relations just to simplify the code
>>>>>(i.e. handle all types of relations in one place).
>>>>>
>>>>>          
>>>>>
>>>>I sometimes change them from blob to text in phhmyadmin just to
>>>>read the content.
>>>>There are however typo3 functions to work with these 'virtual'
>>>>relations. Can't remember them....
>>>>I think it's planned for typo3 version 5 to start with real database
>>>>relations?
>>>>Kicksters does have some functionality for that already called MM
>>>>relation tables.
>>>>        
>>>>
>>>Currently I've only seen the BLOBs contain comma separated lists of
>>>uid's in extensions I build. These are easy to fetch and then use
>>>explode() on them to populate an array with the individual related
>>>UID's. Works like a charm for me, but I may be missing something..
>>>
>>>      
>>>
>>The advantage of having real database relations is that in general
>>retreiving large data structures is faster
>>then calling the RDBM over and over again.
>>Also you can easely make relations in such a way that you can delete
>>releated record automaticly,
>>or use triggers to set a 'deleted' bit on a field. It keeps the
>>database consistend.
>>However, the kickstarter is capable of create MM tables to create mm
>>relations if needed.
>>I didn't see that it's creates a real relation between tables
>>though..... Joe Celko made some exellent books about this subject.
>>    
>>
>
>AFAIK it is used at least in tt_products, where you have sys_products_orders
>containing the order information and sys_products_orders_mm_tt_products for
>the relations to the different items ordered by the client.
>The only disavantage in this case is, that you will get only the current
>item state and not the state the item had while the order was finished. So
>in this case the MM relation doesn't make sense IMHO.
>
>Joey
>
>  
>
I don't see how, but I don't know tt_products

 sys_products_orders_mm_tt_products can affact that, it simple relates 
sys_products_orders to tt_products in a m-m relation. not more not less..

RIes