Re: Foreign key to a partial key
Thank you very much for your answer, David.
If I add the wbs_name field to the products table, it will only defer the issue to now check if the wbs_name is the wbs_name assigned to the project. The constraint you propose could check if the wbs_name and wbs_code combination exist, but it may allow the case where they belong to another project, when for example, copying a product from another project.
I would like the database model to take into account that, but I do not find a way. As I said before, my option would be for an update or insert trigger to check the projects table, find out the wbs_name and check that the product wbs_code belongs to it.
Or maybe another idea I do not see now.
Regards,
Simon Graffe
On Sat, Mar 8, 2014 at 10:07 PM, David Johnston <polobo@yahoo.com> wrote:
> I thought of creating a foreign key constraint this way:
>> The constraint would need to make reference to the wbs_name assigned toAdd the wbs_name column to the products table. Since a code is invalid
> the
> project, but at the table products, no column contains that info.
without knowing which project it belongs to your table definition is wrong.
Then you can create the proper two-column foreign key that references on
primary key on the codes table.
David J.
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