Manipulations like this (backed by the proper relational theory) are at the heart of database query optimizers. The resulting tree is shown in Figure 2.

此类操作(由恰当的关系理论作为支持)是数据库查询优化器的核心所在。

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The relational standardization theory is the relational database development and the design important part.

关系规范化理论是关系数据库开发与设计的重要部分。

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Join dependency in relational data theory is not seldom seen during database systems designing.

本文阐明关系数据规范理论中的连接依赖在设计数据库系统时并不少见。

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