Re: Foreign key as primary key...

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 --- Ofer Nave <onave@xxxxxxxxx.xxx> wrote: 
> Perhaps it would avoid confusion and emails if the
> Class::DBI docs 
> explained that has_a and has_many are for defining
> both sides of a 
> one-to-many relationship, and might_have is for
> defining a one-to-one 
> relationship?  I know this is obvious to any
> intelligent person who has 
> had to go through the implementation of both at
> least once, but at first 
> glance, CDBI is concept-rich and thefore
> overwhelming.
> 
> Sticking a version of this at the top of the "TABLE
> RELATIONSHIPS" 
> section as part of the introduction would probably
> make the whole thing 
> go down quicker and smoother, like a spoonful of
> sugar:
> 
> ---
> Class::DBI directly supports one-to-one and
> one-to-many relationships, 
> and indirectly supports many-to-many relationship. 
> To define a 
> one-to-one relationship, use the 'might_have' method
> from the dominant 
> table (the one you would typically put on the left
> side of a LEFT 
> JOIN).  To define a one-to-many relationship, use
> the 'has_a' and 
> 'has_many' methods, each from the appropriate table.
>  If you have an 
> 'account' table that has a one-to-many relationship
> with a 
> 'monthly_statement' table, you would do something
> like this:
> 
> package Account;
> __PACKAGE__->has_many( monthly_statements =>
> 'MonthlyStatement' );  # 
> adds monthly_statements method
> package MonthlyStatement;
> __PACKAGE__->has_a( account_id => 'Account' );  #
> 'inflates' account_id 
> value into an Account object
> ---
> 
> I'm still new, so I'll let someone else right the
> many-to-many intro 
> paragraph.  :)
> 
> -ofer


That makes a lot of sense - however, doesn't it also
say using has_a on the many side of the relationship
(eg. the MonthlyStatement part) is dangerous if you
are trying to inflate a foreign key which also happens
to be a primary key on the many table. Thus look at
using might_have instead. That's how I read the
current documentation - which is why I was having so
many troubles.

Is there a definitive answer to that conundrum?


>joss


	
	
		
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