建立零或一对多的关系 [英] Model a Zero or One to Many Relationship

问题描述

如何在数据库中建立零或一对多的关系？例如，用户记录可能有也可能没有父级。我的用户表应该有一个t_user.parent_id，还是应该有一个名为t_user_hierarchy的关联表，其中列有t_user_hierarchy.parent_id和t_user_hierarchy.user_id？

How should I model a zero or one to a many relationship in the database? For example, a user record may or may not have a parent. So should my user table have a t_user.parent_id or should I have an associative table called t_user_hierarchy with the columns t_user_hierarchy.parent_id and t_user_hierarchy.user_id?

推荐答案

看这个线程。类似的问题：必需的可空的外键的任何示例？

Look at this thread. Similar problem : Any example of a necessary nullable foreign key?

是否有另一个关联表或可空的外键取决于您的用例。它的主观和取决于你的设计。

Whether to have another association table or nullable foreign key depends on your use case. Its subjective and depends on your design.

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