9 Understanding Queries

This chapter describes how EclipseLink enables you to create, read, update, and delete persistent objects or data using queries in both Jakarta EE and non-Jakarta EE applications for both relational and nonrelational data sources.

This chapter includes the following sections:

• Query Concepts

• About JPQL Queries

• About SQL Query Language

• About the Criteria API

• About Native SQL Queries

• EclipseLink Extensions to Native Query Support

• About Query Hints

• About Query Casting

• About Oracle Extensions for Queries