# How this guide is organized

This guide includes the following sections.

- Performance tips and tricks

  Quick tips on how to improve the performance of Derby applications.

- Tuning databases and applications

  A more in-depth discussion of how to improve the performance of Derby applications.

- DML statements and performance

  An in-depth study of how Derby executes queries, how the optimizer works, and how to tune query execution.

- Selectivity and cardinality statistics

  Information on how the optimizer determines the number of rows that will be scanned from disk when deciding whether to use an index or to scan a particular table.

- Internal language transformations

  Reference on how Derby internally transforms some SQL statements for performance reasons. Not of interest to the general user.

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