Re: *Proper* solution for 1..* relationship?

Wolfgang Keller-2 wrote
> It hit me today that a 1..* relationship can't be implemented just by a
> single foreign key constraint. I must have been sleeping very deeply not
> to notice this.
>
> E.g. there is a table "list" and another table "list_item" and the
> relationship can be described as "every list has at least one
> list_item" (and every list_item can only be part of one list, but
> this is trivial).

Change the cardinality to "0..*" ?

If you want to enforce a view of the data the ensures "1..*" (for list) then
create a view of "list" where only those entries with values in "list_item"
are shown.

Alternately you might simply add a counter column to the list table and use
triggers to increment/decrement the "item_count".

David J.





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