SQL模式-默认为1：很多

Question

How can I specify the default value of a 1:Many relationship ... for example take a user that has 5 phone numbers ... I need to record the "preferred" phone number. Should I use an attribute on the phone_number record to indicate the preferred one - or have a attribute of the user record ( preferred_phone_number for example) that is the primary key from the phone_numbers table ?

Thanks

Answer 1

1. User.preferred_phone : you have zero or one preferred numbers per user.

2. Phone.is_preferred : you may have any amount of preferred numbers per user, without a way to choose the 'most preferred', and even 'preferred numbers' that no user relates to.

So I'd clearly stick with #1.