[V4MD] Object Pointers

[Ruslan Zasukhin]

On 8/7/04 8:28 PM, "Daniel Crowder" <daniel at monumental-i.com> wrote:

Hi Daniel,

> I'm getting ready to start a gargantuan project using Valentina in
> Director. I'm setting everything up currently and have a few questions:
> 
> I have a product table, a media table and a product media link table
> that serves as a link between the two. Fairly basic relational stuff
> (I'm assuming). 

yes

> Instead of using RecIDs in the link table to identify
> the media and products ( and thereby connect the products with the
> media) I was thinking of using two ObjectPtr fields instead. Correct me
> if I'm wrong, but this seems like the *IDEAL* use for ObjectPtr fields.

Yes. 

Just why you say about ObjectPtr and RecID as alternative things?
They work in pair!

    Product Table       { RecID, ... }
    
    Media Table         { recID, .... }

    LinkTable { ObjectPtr to Product, ObjectPtr to Media }

So yes in Link table you must use 2 ObjectPtr fields.
and they will use values from RecID fields of linked records.


> The thing I need a little guidance on is how to use to the objectptr.

Think about it as about SIMPLE ULONG FIELD.

In fact IT IS ulong field.


> For instance: I have   record 55 in the products table - how do I define
> the ObjectPTR value for use in my link table?

Let you want link record 55 of Product, with record 79 of Media.
You do (pseudo code)

    cursor = "SELECT ptr1, ptr2 FROM LinkTable WHERE recID = 0"

    cursor.field( "ptr1" ) = 55
    cursor.field( "ptr2" ) = 79
    cursor.AddRecord()

Or you can use SQL's INSERT

    db.SqlExecute( "INSERT INTO linkTable(prt1, ptr2) VALUES(55, 79) ")


> When any of the records
> are deleted from the products or media tables what is the best way to
> make sure that all records in the link table are removed? Does using
> Object Pointers here provide some built-in benefits?

Yes of course.

Just set both ObjectPtr to have CASCADE deletion.
Then Valentina will a automatically delete records in Link table.

>  Any suggestions and SQL examples are welcome!



-- 
Best regards,
Ruslan Zasukhin      [ I feel the need...the need for speed ]
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e-mail: ruslan at paradigmasoft.com
web: http://www.paradigmasoft.com

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