Hibernate statement used to query whether the correlated object is null

Post posted one year ago: Success.

The person class corresponds to the user class one by one. The ing relationship is as follows:

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1. Private
   User user;
   
2. @ Onetoone
   (Cascade = {cascadetype. All}, mappedby =
   "Person"
   )
   
3. Public
   User getuser (){
   
4. Return
   User;
   
5. }
6. Private
   Person;
   
7. @ Onetoone
   ()
   
8. @ Joincolumn
   (Name =
   "Personid"
   )
   
9. Public
   Person getperson (){
   
10. Return
    Person;
    
11. }

I want to query the list of persons that have not been matched with a user from person.

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1. String hql =
   "From person as P where p. User is null"
   ;
   

But I didn't implement the desired result. The second half of the hibernate statement output by myeclipse is

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1. From person person0 _ Where person0 _. ID is not
   Null
   
   

How is it person0 _. ID?
Is not null. How can I change it to person0 _. ID? How can I write it to implement the functions I want?

Thanks
Maracmo
Answer:

I also encountered this problem today. After studying it, you can use the following statement to find out:
From person as P left join P. User as u where u is null.
By default, Hibernate uses the inner join policy to query Association attributes. Therefore
From person as P where P. User is null statement cannot find the person object with the user attribute being null!