Re: EOModeler join-type vs. optionality

Hi, Zak,

On Mar 8, 2006, at 10:48 AM, Zak Burke wrote:

> In EOModeler, what is the difference between setting a relation's  
> destination to "left outer" in the the Relationship Inspector vs.  
> setting its Optionality to "Optional" in the Advanced Relationship  
> Inspector?

How about, one works everywhere, the other doesn't?

More helpfully, setting Optionality to "Optional" in the advanced  
relationship inspector imposes integrity constraints on the model,  
specifically, if you have:

   A -> B (or A ->> B)

then it will allow you to establish an A with no associated B. If you  
haven't set "Optional", then for each A, you must establish a (or at  
least one) related B as well.

Setting a relation's destination to "left outer" merely indicates  
that when you trigger the fault on that relationship, it will bring  
in not only all A's with a corresponding B, but also all A's that  
have no B's (meaning that the relationship must be first marked  
"Optional").

Be careful with "left outer" in that outer joins tend to work or not  
work inconsistently across database management systems.

Regards,
Jerry

--
__ Jerry W. Walker,
    WebObjects Developer/Instructor for High Performance Industrial  
Strength Internet Enabled Systems

     [email protected]
     203 278-4085        office