String oql = "select * from student in AllStudents where student.age < 20";
OQLQuery query = new OQLQuery(oql);
Object students = query.execute();

Query query = persistenceManager.newQuery(Student.class, "age < 20");
Collection students = (Collection)query.execute();

Query query = database.Query();
query.Constrain(typeof(Student));
query.Descend("age").Constrain(20).Smaller();
IList students = query.Execute();

Example 2: (a) Object Query Language (OQL); (b) JDO Query Language (JDOQL); and (c) db4o SODA (using C#).