Re: Designer/2000 ERD Cardinalities

Mirwais Qader <mq_at_wohl.slh.wisc.edu> wrote:

>Robert Gordon wrote:
>>
>> Could someone please explain the cardinality symbols for D/2000 ERD's?
>> I am familiar with IDEF1X and IE symbologies, but I cannot figure this
>> out - particularly which end is which for the different symbols (and I
>> have RTFM)! Thanks
>>
>> - Robert Gordon
 

>As far as I know, here it is:
 

>Oracle Entity-Relationship Modeling Convention:
>--------------------------------------------------------------------
 

>Each Source Entity [May be or Must be] relationship name [one and only
>one or one or more] destination entity.
 

>--------- Has ----------
>| E1 | >------------- - - - - - | E2 |
>--------- Belongs To ----------
 

>E2 Belongs To One or More E1 or E2 Belongs To atleast one
>possibly many E1
>E1 May have one and only one E2
> ---

This seems to be the opposite of what Jeff said. That is, the section of line closer to E1 corresponds to the crows foot/terminal at the E2 end to form the complete cardinality from E1 to E2??? But in the statement above did you say that the line section and terminal symbol at the E1 end designates the cardinality from E2 to E1??? I'm confused again!

>Optionality:
 

>- - - - - - Optional (May be)
>---------------- Mandatory (Must be)
 

>Degree:
 

>>-------------- One or More (crow's foot)
>---------------- One and only one (straight line)

• Robert Gordon