在接下来的页面中，您要选择在什么地方检索主关键字的值(图28)。

On the next page, you choose where to retrieve the value of the primary key (Figure 28).

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典型的方法是根据实体的主关键字进行查询，因为这可以保证产生一个独一无二的结果。

The typical method is to look up the entity by its primary key, because that will guarantee a unique result.

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注意它们包含了与数据库表列，以及设置的主关键字、关系相对应的区域(图19)。

Notice that they contain fields corresponding to the database table columns and that the primary keys and relationships have been set (Figure 19).

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