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PostgreSQL Developer's Handbook by Hans-Jürgen Schönig, Ewald Geschwinde

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Chapter 13. Classification of Data—Real-World Examples

Selecting data is not the only purpose for relational databases. For reporting, it is essential to perform some sort of aggregation and classification. You have already learned about aggregation functions in this book. A lot of software can be used to deal with classification and aggregation. In this chapter, you learn to work with SQL and the EFEU package. These two ways of working with data are good examples for different concepts.

Working with SQL

In this section, you take a close look at how data can be classified with the help of joins and tables.

In general, classification means that certain values are combined in one group, which is assigned to a new name. How can you tell the database ...

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