Develop Reference

Get specific columns of table in hibernate using addEntity

I am familiar with Java but really new with ORM and Hibernate.
I am using the following query to get the resultset of all columns of a table in hibernate.
(List<Neighborhood>)session.createSQLQuery("SELECT * FROM Neighborhood").addEntity(Neighborhood.class).list();
I want to get only two specific column from this table. I looked up over the internet but not able to find the solution which can be used as a modification of above statement.
I tried the below query but getting - SQLGrammarException: could not extract ResultSet
(List<Neighborhood>)session.createSQLQuery("SELECT neighborhoodName,educationYouth FROM Neighborhood").addEntity(Neighborhood.class).list();
Edit:
Two more attempted queries after #scaryWombat's suggestion. Both give the same exception
First
List list = session.createSQLQuery("SELECT neighborhoodName,educationYouth FROM Neighborhood").list();
Second
String sql = "SELECT neighborhoodName,educationYouth FROM Neighborhood";
SQLQuery query = session.createSQLQuery(sql);
query.setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP);
List results = query.list();
Edit2:
After #Tehmina's solution, I am getting one error - java.sql.SQLException: Column 'educationYouth' not found because educationYouth is an object of class name "EducationYouth".
In the Neighborhood table there is no column with name educationYouth but all the column from EducationYouth class.

Try this
(List<Neighborhood>)session.createSQLQuery("SELECT * FROM Neighborhood").list();
To avoid the overhead of using ResultSetMetadata, or simply to be more explicit in what is returned, one can use addScalar():
(List<Neighborhood>)session.createSQLQuery("SELECT * FROM Neighborhood").addScalar("neighborhoodName", Hibernate.STRING).addScalar("educationYouth", Hibernate.STRING);
Or try this
Hibernate automatically converts the data into appropriate type. The automatic conversion does not work in all cases and in that case we have an overloaded version of addScalar():
SQLQuery q = session.createSQLQuery("SELECT * FROM Neighborhood");
q.addScalar("neighborhoodName");
q.addScalar("educationYouth");
List<Object[]> rows = q.list();
for (Object[] row : rows) {
System.out.println(row[0] + " " + row[1] );
Don't forget to check in the hibernate config file
<!--hibernate.cfg.xml -->
<property name="show_sql">true</property>
I hope it would resolve your error.

How can I correctly implement an Hibernate SQL query starting from an SQL query that count the number of rows?

I am absolutly new in Hibernate and I have the following problem.
I have this standard SQL query:
SELECT count(*)
FROM TID003_ANAGEDIFICIO anagraficaEdificio
INNER JOIN TID002_CANDIDATURA candidatura
ON (candidatura.PRG_PAR = anagraficaEdificio.PRG_PAR AND candidatura.PRG_CAN = anagraficaEdificio.PRG_CAN)
INNER JOIN TID001_ANAGPARTECIPA anagPartecipa ON(anagPartecipa.PRG_PAR = candidatura.PRG_PAR)
INNER JOIN anagrafiche.TPG1029_PROVNUOIST provNuovIst ON (provNuovIst.COD_PRV_NIS = anagPartecipa.COD_PRV_NIS)
WHERE anagraficaEdificio.FLG_GRA = 1 AND provNuovIst.COD_REG = "SI";
This works fine and return an integer number.
The important thing to know is that in this query the only
parameter that can change (inserted by the user in the frontend of a webappplication) is the last one (this one: provNuovIst.COD_REG = "SI").
So, the application on which I am working use Hibernate and the requirement say that I have to implement this query using Hibernate Native SQL, I have found this tutorial:
http://www.tutorialspoint.com/hibernate/hibernate_native_sql.htm
that show this example:
String sql = "SELECT * FROM EMPLOYEE WHERE id = :employee_id";
SQLQuery query = session.createSQLQuery(sql);
query.addEntity(Employee.class);
query.setParameter("employee_id", 10);
List results = query.list();
that, from what I have understand (correct me if I am doing wrong assertion), involves the use of an Employee model class. So th prvious query first define the query (using the :param_name syntax for the parameter), then create an SQLQuery Hibernate object, add the class used for the result, set the previous parameter neam and finally obtain a List (that I think Hibernate create as something like an ArrayList) with the retrieved object.
My problem is that I simply I have to obtain an integer value (because I have a SELECT count(*), so I will obtain an integer value and not a set of rows).
So how can I correctly use the Hibernate Native SQL to implement my SQL query into my Hibernate repository class?

Use SQLQuery.uniqueResult to retrieve a single value from the query:
String sql = "SELECT count(*) ...";
SQLQuery query = session.createSQLQuery(sql);
// set parameters...
int count = ((Number)query.uniqueResult()).intValue();

NamedQueries in JPA

From what I know, UPDATE and DELETE can be done by NamedQueries.
However,
void updateName (int ID, String name) {
EntityManager entityManager =
Persistence.createEntityManagerFactory("uPU").createEntityManager();
Query query = entityManager.createNamedQuery("Users.updateName");
query.setParameter("name", name);
query.setParameter("id", ID);
}
isn't doing the update.
The named query is as follows:
#NamedQuery(name = "Users.updateName", query = "UPDATE Users u SET u.name = :name "
+ "WHERE u.id = :id "),
A similar thing going on with DELETE.
Nothing wrong with SELECT on Namedqueries.
Is there something more to altering the contents of an SQL table with NamedQueries?
//================================
ADD:
i'm using a namedquery.
From what I know, opening the transaction and commiting it is not necessary on namedQueries.
query.executeUpdate();
gives a runtime error.
//================================
ADD2:
The code is giving no compile or runtime errors except to that addition suggested by DataNucleus below. see my previous edition above regarding that suggestion.

Thought about actually executing the query? All you've done there is create it.
query.executeUpdate()
http://www.datanucleus.org/products/accessplatform/jpa/jpql.html#JPQL_UPDATE_Queries

Creating inner query in hibernate

how to add a set parameter() metheod inside the inner query in hibernate?
I have try to do like this but already have a errors
this is my code
Query query=session.createQuery("select eq.euipmentName,eq.type from Euipment eq where eq.id in(select euipment from Quotation qt where qt. supQuotation=:ids)");
query.setParameter("ids",id);
list = (List<Euipment>)query.list();

I've done some corrections about your query:
1. qt. supQuotation has a space, I've removed
2. euipment in you sub query haven't alias, I add qt
String hql =
"select eq.euipmentName,eq.type " +
" from Euipment eq " +
" where eq.id in (select qt.euipment from Quotation qt where qt.supQuotation = :ids)";
Query query = session.createQuery(hql);
query.setParameter("ids",id);
list = (List<Euipment>)query.list();
Tell me, if it's OK
If not OK, please post here the error, and check if you have put in hibernate mappping file your classes

From Hibernate Documentation:
Execution of native SQL queries is controlled via the SQLQuery
interface, which is obtained by calling Session.createSQLQuery().
createQuery() creates Query object using the HQL syntax.
createSQLQuery() creates Query object using the native SQL syntax.
So replace createQuery with createSQLQuery for native SQL query.

Try with Criteria
Criteria c = getSession().createCriteria(Euipment.class, "e");
c.createAlias("e.quotation", "q"); // inner join by default
c.add(Restrictions.eq("q.supQuotation", id));
list = (List<Euipment>)c.list();

Get record with max id, using Hibernate Criteria

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?

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

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.

Use
addOrder(Order.desc("id"))
and fetch just the first result :)

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.

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);

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);
}

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) );

For the max() function in hibernate:
criteria.setProjection(Projections.max("e.encounterId"));