If I'm creating a Customer table that includes contact info and I require either a phone number or an email address, how can I ensure that both fields cannot be left blank? In other words, a customer's record can have an entry in the Phone column or in the Email column or in both, but it must have at least one or the other. How do I use the NOT NULL constraint so that either column may be null, but not both in the same record?
Thank you
Chillay
Thank you
Chillay