The linkage between the application and database tiers typically takes the form of SQL calls into a relational database.

应用程序和数据库层之间的联接通常采用关系数据库中的SQL调用格式。

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Typically, a module also accesses an underlying database. Some experience with a relational database and SQL is helpful, as well.

通常，模块也会访问底层数据库，因此，关系数据库和SQL方面的经验也会对您有所帮助。

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We can embrace the relational database, dropping down into SQL as needed and staying above it when convenient.

我们可以包含关系数据库，需要时转入SQL并在适当的时候退出。

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This traditional database platforms, known as relational database management systems (RDBMS) all use a language called SQL (structured query language).

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