This tip starts with a simple description of the problem: defining a composite database key.
本技巧从问题的简单的描述开始：定义组合数据库键。
This is a key, similar to a database key structure that identifies a particular cache entry as unique.
这是一个键值，如同数据库里的键结构，唯一地标识每一个高速缓存条目。
This identifier, most often a database key, can be generated and sent to the client as one of the URL parameters.
这个标识符(通常是数据库键)能够作为该url参数之一而生成并发送到客户机。
If you extract records from a database to create the XML documents, you can transfer the database key directly to the key attribute of the address_rec element.
如果您从一个数据库提取一些记录来创建XML文档，您可以将数据库键直接传输到address_rec元素的key属性。
The table must match the definition of your attributes; for example, the primary database key for the equations table must be the primary key of the Persistent class as well.
表必需与属性定义匹配，例如，等式表的主数据库键必须也是 Persistent类的主键。
With the launch of the application, a global database key is generated and stored in the keychain.
随着应用程序的启动，生成一个全局数据库密钥并存储在钥匙串中。
With the launch of the application, a global database key is generated and stored in the keychain.
随着应用程序的启动，生成一个全局数据库密钥并存储在钥匙串中。
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