How to avoid duplicates in the unique composite key, when one of the values NULL?
question incorrect and was therefore closed. remove it please
asked April 4th 20 at 13:04
The program works right, Bob+ null in the phone and then in the mail will not work, maybe Bob + null will repeat you the key. And what you don't like option 3 m fields?
to normalize relations. if you want to record phones X and Y addresses for the same user, then it should be done differently
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