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 Post subject: Criteria nested select using max of child collection
PostPosted: Mon Sep 05, 2016 5:21 am 
Newbie

Joined: Mon Sep 05, 2016 4:18 am
Posts: 3
Hi,
I have:

Code:
@Entity
public class Parent implements Serializable {
   private static final long serialVersionUID = 1L;

   @Id
   private Integer id;
   private String name;
   @ManyToMany(fetch = FetchType.EAGER, cascade = CascadeType.MERGE)
   @JoinTable(name = "PARENT_CHILD", joinColumns = {@JoinColumn(name = "PARENT_PID")}, inverseJoinColumns = {@JoinColumn(name = "CHILD_PID")})
   @OrderBy("persistenceId DESC")
   private List<Child> childs = new ArrayList<Child>();
}


Code:
@Entity
public class Child implements Serializable{   
   private static final long serialVersionUID = 1L;

   @Id
   private Integer id;   
   private String name;
   private Integer age;
}


----------------------
Parent
----------------------
id |name
----------------------
1 |John
2 |Kevin
3 |David

----------------------
Child
----------------------
id |name |age |parent_id
----------------------
1 |Marc |18 |1
2 |Jim |10 |1
3 |Bob |17 |1
4 |Steve |17 |2
5 |Anne |21 |2
6 |Simon |23 |2
7 |Carl |25 |3
8 |Matt |17 |3
9 |Jason |3 |3

I want only the parent where the last child inserted in DB has 17 years old.

Expeted result is:
1 |John
The 3rd child Bob's has 17 years old.

With hibernate Criteria, what is the solution?

Thanks in advance


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 Post subject: Re: Criteria Many to Many inner join: search in last record
PostPosted: Mon Sep 05, 2016 5:34 am 
Hibernate Team
Hibernate Team

Joined: Thu Sep 11, 2014 2:50 am
Posts: 1433
First of all, I'd recommend you switch to LAZY instead of EAGER because EAGER is bad for collections.

Code:
@ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.MERGE)


Second, you need to think of the SQL query first prior to trying to translate it to Criteria. What SQL query have you come up with?

_________________
If you liked my answer, you are going to love my High-Performance Java Persistence book and my blog as well.


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 Post subject: Re: Criteria Many to Many inner join: search in last record
PostPosted: Mon Sep 05, 2016 5:58 am 
Newbie

Joined: Mon Sep 05, 2016 4:18 am
Posts: 3
In SQL is:

Code:
SELECT p.*, c.*
FROM Parent p
INNER JOIN Parent_Child pc ON p.id = pc.Parent_pid
INNER JOIN Child c ON c.id = pc.Child_pid
WHERE c.id = (
    SELECT Max(pc1.Child_pid) as id1
    FROM Parent_Child pc1
    WHERE pc1.Parent_pid = p.id
) AND c.age = 17;


Thanks


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 Post subject: Re: Criteria Many to Many inner join: search in last record
PostPosted: Mon Sep 05, 2016 6:28 am 
Hibernate Team
Hibernate Team

Joined: Thu Sep 11, 2014 2:50 am
Posts: 1433
First, this SQL query can be translated to HQL like this:

Code:
SELECT p.
FROM Parent p
JOIN p.childs c
WHERE c.id = (
    SELECT max(c1.id) a
    FROM Child c1
    WHERE c1.parent = p
) AND c.age = 17;


For Criteria, try this query:

Code:
DetachedCriteria innerCriteria = DetachedCriteria.forClass(Child.class, "inner")
    .add(Restrictions.eqProperty("inner.parent.id","upper.id"))
    .setProjection(Projections.projectionList().add(Projections.max("inner.id")));

DetachedCriteria outerCriteria= DetachedCriteria.forClass(Parent.class, "upper");
outerCriteria.createAlias("upper.childs", "children");
outerCriteria.add(Subqueries.propertyEq("children.id", innerCriteria ));
outerCriteria.add(Restrictions.eqProperty("children.age", 17));

List<Parent> parents = outerCriteria.getExecutableCriteria(session).list();

_________________
If you liked my answer, you are going to love my High-Performance Java Persistence book and my blog as well.


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 Post subject: Re: Criteria nested select using max of child collection
PostPosted: Mon Sep 05, 2016 10:33 am 
Newbie

Joined: Mon Sep 05, 2016 4:18 am
Posts: 3
Thanks,
I try it.

Jenna


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 Post subject: Re: Criteria nested select using max of child collection
PostPosted: Thu Sep 08, 2016 8:53 am 
Hibernate Team
Hibernate Team

Joined: Thu Sep 11, 2014 2:50 am
Posts: 1433
It worked, right?

_________________
If you liked my answer, you are going to love my High-Performance Java Persistence book and my blog as well.


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