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JPA Join with aggregate function

I am a beginner when it comes to JPA and I am struggling to write the proper entity classes for my database structure.
Firstly, here are my tables:
create table article (
id varchar(100) not null primary key,
title varchar(255) not null
)
create table article_provider (
providerId varchar(60) not null,
articleId varchar(100) null,
isOnSale BOOL NOT NULL,
constraint article_provider_articleid_fk foreign key (articleId) references article (id) on update cascade on delete cascade
)
As you can see I have a one-to-many relationship (every article can have 0..n providers).
Now when accessing articles I would also like to know, if the article is on sale by any of it's providers. For this I would use the following SQL query:
SELECT article.*, MAX(article_provider.isOnSale) AS isOnSale FROM article
LEFT JOIN article_provider ON article.id = article_provider.articleId
GROUP BY article.id
How would I best go about fetching this type of result using Hibernate/JPA?

Your query is not right -- you use attributes in SELECT clause that are not in GROUP BY clause, but for example to select Article.id + MAX(whatever) you can use something like:
CriteriaBuilder builder = entityManager.getCriteriaBuilder();
CriteriaQuery<Article> query = builder.createQuery(Article.class);
Root<Article> root = query.from(Article.class);
Join<Article, ArticleProvider> join = root.join(Article_.provider, JoinType.LEFT);
query.multiselect(root.get(Article_.id), builder.max(sale));
query.groupBy(root.get(Article_.id));
// query will return collection of scalar attributes (ID + Number)
Object result = entityManager.createQuery(query).getResultList()
To select exactly Article.* + MAX(sales) you would need to use the above as a subquery and join again with Article entity.
But there are simillar of examples elsewhere: How do I write a MAX query with a where clause in JPA 2.0?
EDIT:
another tip: https://www.thoughts-on-java.org/hibernate-tip-subquery-criteriaquery/
correction/clarification: I have only assumed you want to use Criteria API where subquery and combining the results for Hibernate is probably the only way. But you may try to use JPA query language and/or different provider where subquery with multiple results can be used -- jpa eclipselink subquery in from clause

How to rewrite sql statement to work with hibernate?

I'm using PostgreSQL in my java application without ORM. I want to go further and add Hibernate to my project. I have this sql query which I add to PreparedStatement() and it returns a number.
SELECT COUNT(pr.id) FROM prisoner pr
JOIN cell c ON c.id = pr.cell_id
JOIN prison p ON p.id = c.prison_id
WHERE p.id = ?
I'm new to Hibernate. How would you suggest me to rewrite this statement to work with Hibernate? Should I use HSQL, or criteria or query or something different ?

You can do it Either of following way.
1) Keep you query as it and use nativeSQL for hibernate.
hibernate native query, count
2) make model of all your join table and put hibernate query.

How to update 2 tables using one query in JPA native query?

I have 2 tables TABLE1 and TABLE2.Table1 is having name and Table2 is having email and Phone.
To get the name,email and phone,I query as below
query = entityManagerUtil.createNativeQuery("select s.Name,c.Phone1,c.Email1 from Table1 s,Table2 c where c.id= s.NodeID and s.NodeID =21")
Now my next requirement is to update name,email and phone.As these parameters are present in different tables so I am searching for single query which will update 2 tables.Unfortunately I am using sql server and there is no way to update 2 tables using single query
So I am thinking to use #Transactional and 2 queries to update 2 tables like the follow
#Transactional
public void updateDetails()
{
Query query1= entityManagerUtil.entityManager.createNativeQuery("update Table1 set Name='' where id in (select NodeID from Table 2) and NodeID=21");
Query query2= entityManagerUtil.entityManager.createNativeQuery("update Table2 set Email='' and phone1='' where NodeID in (select id from Table 2) and NodeID=21");
query1.executeUpdate();
query2.executeUpdate();
}
Is there any other better way to update 2 tables?

you can use JDBCTemplate
http://sujitpal.blogspot.com.es/2007/03/spring-jdbctemplate-and-transactions.html
It allows to do multiple queries with one connection, so you save some time instead of doing it twice.

Why don't you use Hibernate entities for that. Just load the entities associated with Table1 and table2, modify them and let the automatic dirty checking mechanism to update the tables on your behalf. That's one reason for using an ORM by the way.

Hibernate Criteria filter Entity where ManyToMany relation contains multiple objects

I need help with Hibernate Criteria API.
I have a class Job that contain a list of Skill in ManyToMany relationship.
I need to select jobs based on a skill list given as parameter.
I've tried with Restriction.in("skill.id",ids) but this gives me wrong list.If i've selected 2 skills in search form i want the jobs that contain BOTH of them,so i need somehow to implement AND clause.
I've tried with Conjunction:
Conjunction and = Restrictions.conjunction();
for(Skill skill:job.getSkills()){
and.add(Restrictions.eq("skill.id",skill.getId()));
}
And this:
Criteria crit = criteria.createCriteria("skills",JoinType.LEFT_OUTER_JOIN);
for(Skill skill:job.getSkills()){
crit.add(Restrictions.eq("id", skill.getId()));
}
but it creates same alias for skill and it gives me no result.
sql is and (skill1_.ID=? and skill1_.ID=?)
Can anyone help me with this ?thanks
UPDATE:
HQL Query will be like:
select a from Job a where exists (select skill1.id from Skill skill1 join skill1.jobs r where r.id=a.id and skill1.id=1) and exists (select skill2.id from Skill skill2 join skill2.jobs r where r.id=a.id and skill2.id=4)
I need Criteria based on this.

for(Skill skill:job.getSkills()){
DetachedCriteria subquery = DetachedCriteria.forClass(Skill.class,"skill");
subquery.add(Restrictions.eq("id",skill.getId()));
subquery.setProjection(Projections.property("id"));
subquery.createAlias("jobs", "job");
subquery.add(Restrictions.eqProperty("job.id", "Job.id"));
criteria.add(Subqueries.exists(subquery));
}
I managed to solve it.now it works perfect.

How to map native query to one model class?

Hi I´m using Eclipselink and I did a native query to select some fields of 2 tables. I mapped my table Logins in a model class. I would not like to map my table "B" because I need only 2 fields of this table on my sql result.. can I map this 2 fields in my Logins table to my sql result ?
My sql is this:
select l.login_id, s.lugarcerto,s.vrum, l.username, l.first_name, l.last_name, l.phone, l.fax_number, l.address, l.zip,
l.address2 as 'birth_date', l.city as 'cpf_cnpj'
from Logins l
join (select se.login_id, lugarcerto = min(case when se.service = 'IM' then '1' end), vrum = min(case when se.service = 'VE' then '1' end)
from (select distinct ad.login_id, substring(ap.Rate_code,(CHARINDEX('-', ap.Rate_code)+1),2) as 'service'
from Ad_Data.dbo.ad ad
join Ad_Data.dbo.ad_pub ap on (ad.ad_id = ap.ad_id)
where ap.ad_type =1) se
group by se.login_id) s on (s.login_id = l.login_id)
I did map Logins table and I want to map s.lugarcerto and s.vrum to my SQL query result.
There´s anyway to just add it to my Logins model ?

Not without having mappings for the attributes you want those values put into, and not without causing problems with them being cached in the entity.
Why not just return the values beside the entity, much like you would with a JPQL query such as: "Select l, subquery1, subquery2 from Logins l" ie:
Query q = em.createNativeQuery(yourQueryString, "resultMappingName");
And in the entity, include the annotation:
#SqlResultSetMapping(name="resultMappingName",
entities={#EntityResult(entityClass=com.acme.Logins.class, )},
columns={#ColumnResult(name="LUGARCERTO"), #ColumnResult(name="VRUM")}
)
Best Regards,
Chris