Re: Foreign Key Constraints

[Colin Bull]

kyuubi@stripped wrote:

>Hi, I am trying to use the foreign key constraints from InnoDB
>and creating indexes is a requirement for foreign key.
>The problem is that by creating index for my foreign key,
>it does not allow my foreign key to have null or blank values which my records will
> have.
>For eg. a BorrowerID is a foreign key on a Book table, but when the book is not
> borrowed, 
>the BorrowerID will be null and I can't seem to import the data containing null values
> for the foreign key.
>Is there a way to solve this? 
>Thanks.
>
>
>
>  
>
I think you have missed the point of a foreign key constraint. It is to 
ensure referential integrity. A constraint stops you doing things, ie 
entering a value that does not exist in another table.

Or create a borrower called NO-ONE and always change the borrower to 
this when a book is returned.

Or just use an outer join on an indexed field when doing reports is 
easiest and no constraint.

Colin Bull