总参与和递归关系的表示法有什么区别？ [英] What's the difference in notation for total participation and recursive relation?

问题描述

以下ER图中的双线表示总参与或递归关系吗？

Does the double line in the following ER diagrams means total participation or recursive relation?

有人可以告诉我两者的符号区别吗？

Could anyone tell me the notation difference for both?

推荐答案

总参与度：：集合中的每个实体都参与了某种关系关联（或元组）。

Total Participation: Every entity in the set is involved in some association (or tuple) of the relationship.

递归关系：与自己相关的实体集。

Recursive Relationship: An entity set relating to itself.

在递归关系中，最常见的含义是它们表示实体可以具有的不同类型的角色（例如，不同的角色通过在每行上方写每个角色来建立关系。

Most commonly in recursive relationships they indicate the different types of roles an entity can have (e.g., the different ways it can participate) in a relationship by writing each role above each line.

将在 Course 表中，而关系表为先决条件

An example of this would be in a Course table with a relational table of Prerequisites

课程可以是先决条件和课程，您将在每行上写出来。

A Course could be both the Prerequisite and the Course and you would write those on each line.

这里是另一个示例。

假设您的教科书遵循类似的模式，则我认为这些实际上是总参与限制。

Assuming your textbook follows a similar pattern, I would assume that these are in fact total participation constraints.

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