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I am currently enrolled in the online Oracle Academy Database Design Course, which briefly talks about the concept of nontransferable relationships. I understand the concept behind them, but the course's vague details left me with a few of questions.

  1. Can nontransferable relationships exist between entities which are connected with a 1:1 or M:M relationship? All of the example provided by Oracle depicted 1:M relationships.

  2. Can the diamond used to represent the nontransferable relationship be drawn on either end of the relationship, whether they are optional or mandatory? I believe they can only appear on the mandatory end of the relationship, but I want to be sure.

  3. Similarly, can the diamond used to represent the nontransferable relationship potentially appear on BOTH ends of the relationship?

The following are a couple of examples provided by the Oracle Academy: Example1 Example2

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  1. 我不确定，但如果您考虑某些 1:1 关系，它们是不可转让的。例如，一个人只能拥有一本护照。护照不能在人与人之间转让。我不确定多对多，但我可以想到一个例子——你可以有一群人写系列书。这将是多对多的，并且作者身份不能转让给其他人。这可能不是一个很好的例子。

  2. 钻石可以画在任何一边，但通常它出现在强制端，所以我总是把它放在那端。

  3. 我从未见过两端的钻石。

于 2017-08-01T03:32:07.277 回答