Getting Started: Java - Google App Engine - Google Code. Java Persistent Objects - JDO Queries. JDOQL - JDO Database Query Language. There are various ways to retrieve objects from an ObjectDB database, as shown in section 6.3.
An Extent, for instance, can be used to retrieve all the instances of a specified persistent class. When a more selective retrieval is needed, JDOQL (JDO Query Language) is used. JDO Community Process: JDO 2 Queries - Part 1. Welcome to Part I of my four-part series on JDOQL.
The articles in this series illustrate the new capabilities which the forthcoming JDO 2.0 standard is bringing to JDOQL. The series is comprised of: JDOQL Part I - New operator and method support, paging of query results, and datastore-delegated "deletion by query". JDOQL Part II - Projection, aggregation and the grouping ad de-duplication (making distinct) of query results.