Issue with selecting max id rows using criteria query / hibernate query?

问题

I am unable to select the rows where TestId is max for respective student, I wrote the code as follows which does not get the required output. my code is as follows,

Criteria c = sessionFactory.getCurrentSession().createCriteria(student.class).setProjection(Projections.projectionList().add(Projections.property("answer"),"answer"));
c.add(Restrictions.eq("surveyId",send_Survey));
//c.add(Restrictions.eq("testId", "1" ));
//c.setProjection(Projection.max("testId"));
c.addOrder(Order.desc("testId"));
c.add(Restrictions.eq("questionid",FinalQuestionsOne));
List<String> age=c.list();

My table structure is as follows,

I need the following output. select the answer column for max TestId's. How can I get the output using criteria query

回答1:

So I think what you're trying to get can be achievedd by the following sql:

SELECT TestId, MAX(answer) WHERE questionId = 1 GROUP BY TestId;

You should be able to achieve this with the following Hibernate:

sessionFactory.getCurrentSession().createCriteria(student.class).setProjection(Projections.projectionList()
                        .add(Projections.property("TestId"), "TestId")
                        .add(Projections.groupProperty("TestId"))
                        .add(Projections.max("answer")));

来源：https://stackoverflow.com/questions/23489359/issue-with-selecting-max-id-rows-using-criteria-query-hibernate-query