Chapter 3. Mapping to Relational Databases

The role of the data source layer is to communicate with the various pieces of infrastructure that an application needs to do its job. A dominant part of this problem is talking to a database, which, for the majority of systems built today, means a relational database. Certainly there’s still a lot of data in older data storage formats, such as mainframe ISAM and VSAM files, but most people building systems today worry about working with a relational database.

One of the biggest reasons for the success of relational databases is the presence of SQL, a mostly standard language for database communication. Although SQL is full of annoying and complicated vendor-specific enhancements, its core syntax is ...

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