使用条件查询/休眠查询选择最大ID行的问题？ [英] Issue with selecting max id rows using criteria query / hibernate query?

问题描述

我无法选择相应学生的TestId为max的行，我编写了如下代码，但未获得所需的输出。我的代码如下，

 条件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（）; 
  

我的表结构如下，

我需要以下内容输出。选择最大TestId的答案列。如何使用条件查询获取输出

解决方案

所以我认为您可以通过以下sql来实现：

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

您应该可以使用以下Hibernate实现此功能：

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

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

解决方案

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")));

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