Re: Foreign Key Constraints

[Colin Bull]

[EMAIL PROTECTED] 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
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