每个组的休眠条件maxResults

Question

I have a table with rows internalId, value and date. There are multiple entries with the same internalId but different date. I'm only interested in the most recent value of each internalId. How do I manage it with Criteria? This is the my current base code:

Criteria criteria = session.createCriteria(myClass.class); 

ProjectionList projList = Projections.projectionList(); 
projList.add(Projections.property("internalId"));
projList.add(Projections.property("value")); 
projList.add(Projections.property("date")); 

criteria.setProjection(projList);
criteria.add(Restrictions.in("internalId", internalIds));
List list = criteria.list();

Answer 1

From what I understand, what you want is to accomplish i something like this:

SELECT 
    internalId, 
    value, 
    max(date) as date 
FROM 
    table 
WHERE 
    internalId IN (1, 2, 3, 4 ...) 
GROUP BY 
    internalId

This can be achieved with the Projections max function:

projList.add(Projections.max("date"));

and the groupProperty function

projList.add(Projections.groupProperty("internalId"))

For reference: http://docs.jboss.org/hibernate/orm/3.5/reference/en/html_single/#querycriteria