How does one set the Type and the Degree of Participation

[Ruslan Zasukhin]

on 4/28/03 8:37 PM, Douglas Wagner at hdmw at macdev.co.uk wrote:

Hi Douglas,

Good questions.

> Hello:
> I'm using the definitions for type and degree from, "Database Design
> for Mere Mortals", Hernandez. ISBN 0-201-75284-0
> 
> Here are the definitions:
> 
> Type of Participation:
> Table_A's participation is mandatory if one must enter at least one
> record into Table_A before one can enter records into Table_B.
> 
> Table_A's participation is optional if one is not required to enter
> any records into Table_A before one can enter records into Table_B.

> Degree of ParticIpation:
> The degree of participation determines the minimum number of records
> that a given table must have associated with a single record in the
> related table and the maximum number of records that a given table is
> allowed to have associated with a single record in the related table.
> 
> Can these conditions be built into a Valentina DB and if so, how?

Okay I see.

Participation not implemented.

Degree:
1) if you make POINTER field in the MANY table (B) to be unique,
    then you get 1 : 1 link.

2) otherwise it is 1 : M link.
    
Theory allow speak about e.g. 1 : 2 link.
I.e. When we define some n value.
This is not possible in current version of Valentina.
Actually this is rare feature for DB.
But I hope implement it for Valentina also.

For now you can try do this on your app level.


-- 
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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