Get record with max id, using Hibernate Criteria

问题

Using Hibernate's Criteria API, I want to select the record within a table with the maximum value for a given column.

I tried to use Projections, creating an alias for max(colunName), then using it in restrictions.eq(), but it keeps telling me "invalid number".

What's the correct way to do that with Hibernate?

回答1:

You can use a DetachedCriteria to express a subquery, something like this:

DetachedCriteria maxId = DetachedCriteria.forClass(Foo.class)
    .setProjection( Projections.max("id") );
session.createCriteria(Foo.class)
    .add( Property.forName("id").eq(maxId) )
    .list();

References

Hibernate Core Reference Guide
- 15.8. Detached queries and subqueries

回答2:

I found that using addOrder and setMaxResults together worked for me.

Criteria c = session.createCriteria(Thingy.class);
c.addOrder(Order.desc("id"));
c.setMaxResults(1);
return (Thingy)c.uniqueResult();

Using the MySQL dialect, this generates a SQL prepared statement about like this (snipping out some of the fields):

select this_.id ... from Thingy this_ order by this_.id desc limit ?

I am not sure if this solution would be effective for dialects other than MySQL.

回答3:

Use

addOrder(Order.desc("id"))

and fetch just the first result :)

回答4:

HQL:

from Person where person.id = (select max(id) from Person)

Untested. Your database needs to understand subselects in the where clause.

Too lazy to find out if/how such a subselect can be expressed with the criteria api. Of course, you could do two queries: First fetch the max id, then the entity with that id.

回答5:

The cleaner solution would also be :

DetachedCriteria criteria = DetachedCriteria.forClass(Foo.class).setProjection(Projections.max("id"));
Foo fooObj =(Foo) criteria.getExecutableCriteria(getCurrentSession()).list().get(0);

回答6:

    Date maxDateFromDB = null;
    Session session = (Session) entityManager.getDelegate();
//Register is and Entity and assume maxDateFromDB is a column.
//Status is another entity with Enum Applied.
//Code is the Parameter for One to One Relation between Register and Profile entity.
    Criteria criteria = session.createCriteria(Register.class).setProjection(Projections.max("maxDateFromDB") )
    .add(Restrictions.eq("status.id", Status.Name.APPLIED.instance().getId()));
    if(code != null && code > 0) {
        criteria.add(Restrictions.eq("profile.id", code));
    }
    List<Date> list = criteria.list();

    if(!CollectionUtils.isEmpty(list)){
        maxDateFromDB = list.get(0);
    }

回答7:

To do it entirely with Detached Criteria (because I like to construct the detached criteria without a session)

DetachedCriteria maxQuery = DetachedCriteria.forClass(Foo.class)
    .setProjection( Projections.max("id") );
DetachedCriteria recordQuery = DetachedCriteria.forClass(Foo.class)
    .add(Property.forName("id").eq(maxId) );

回答8:

For the max() function in hibernate:

criteria.setProjection(Projections.max("e.encounterId"));

来源：https://stackoverflow.com/questions/3900105/get-record-with-max-id-using-hibernate-criteria

标签

java

hibernate

criteria