如何在ERD上确定强弱关系? [英] How to identify a strong vs weak relationship on ERD?

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问题描述

虚线表示关系很牢固,而实线表示关系很弱。在下图中,我们如何确定 Room Class 实体之间的关系牢固。是因为 Room 实体具有常规键(非复合键)吗?

A dashed line means that the relationship is strong, whereas a solid line means that the relationship is weak. On the following diagram how do we decide that the relationship between the Room and Class entities is strong. Is it because Room entity has a regular key (non-composite)?

推荐答案

当且仅当我们有依赖于ID的关系时,我们才画一条实线

We draw a solid line if and only if we have an ID-dependent relationship; otherwise it would be a dashed line.

考虑一个弱但不依赖于ID的关系;否则,它会成为虚线。我们画一条虚线是因为这种关系很弱。

Consider a weak but not ID-dependent relationship; We draw a dashed line because it is a weak relationship.

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