Re: Non Compulsory toOne Relationships, Propergating Primary Key
Re: Non Compulsory toOne Relationships, Propergating Primary Key
- Subject: Re: Non Compulsory toOne Relationships, Propergating Primary Key
- From: Chuck Hill <email@hidden>
- Date: Wed, 12 Dec 2007 16:30:23 -0800
On Dec 12, 2007, at 4:25 PM, Owen McKerrow wrote:
On 08/12/2007, at 7:02 AM, Art Isbell wrote:
On Dec 7, 2007, at 8:51 AM, Chuck Hill wrote:
On Dec 6, 2007, at 11:50 PM, Art Isbell wrote:
A to-one relationship from one foreign key to a primary key
Typo: should read "from a primary key to a primary key"
must always have exactly one row in the destination entity—if
this isn’t guaranteed to be the case, use a to-many
relationship. This rule doesn’t apply to a foreign key to
primary key relationship where a null value for the foreign key
in the source row indicates that no row exists in the destination.
I copied and pasted the above, so it's not a typo in the general
case. However, in this specific case, the foreign key is the
primary key, so "from a primary key to a primary key" applies.
Aloha,
Art
So what this seems to be saying is that WebObjects supports 0..X or
1..1 relationships but not 0..1 ?
Mmmm, no. :-) A FK to a PK relationship is (can be) 0..1, PK to PK
can't so Propogate Primary Key can't be used with optional
relationships.
Chuck
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