The concept of inheritance throws in several interesting twists when saving objects into a relational database.

在将对象保存到关系数据库中时，继承的概念中发生几个有趣的问题。

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Data access objects are responsible for operating on objects that hold data stored in a relational database.

数据访问对象负责对持有数据(存储在关系数据库中)的对象进行操作。

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Again, just like relational database management systems (RDBMS), objects and RDF are similar in some ways and different in others.

另外，像关系数据库管理系统（RDBMS）一样，对象和 RDF 在一些方面相似而在其他方面不同。

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With a relational database, you start with the domain objects, and represent them in a way that guarantees that virtually any query can be expressed.

FORBES: What You Need to Know About NoSQL Databases