I'm trying to represent this:

  • A message can be sent to one or more recipients.
  • A user (recipient) can receive zero or more messages (but he/she could receive a message only once).

Is my database design correct?

enter image description here

2 Answers 2


enter image description here

In nutshell that what you are looking for. You do need composite primary key "binding" those 2 FK in intersection table. (all attributes are omitted for brevity)

USERS can receive zero - or - more messages Messages can be sent to one - or - more users.


Tool i used to generate image is a bit buggy - line bewteen mail_box and Users should be dotted.

  • A message has a sender and one or more recipient. Where is the sender here?
    – VansFannel
    May 31, 2014 at 6:32
  • I have updated my question with a better diagram.
    – VansFannel
    May 31, 2014 at 6:53

The answer for my question is YES. With this model, I can represent a message that could have only one recipient.

I have found this question and it has the same model than mine.

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