Difference between JOIN and JOIN FETCH in JPA

 
  

    where to use a regular JOIN and where a JOIN FETCH？ For example, if we have these two queries 
   
 
    
FROM Employee emp
JOIN emp.department dep
  
and 
FROM Employee emp
JOIN FETCH emp.department dep
  
Is there any difference between them? If yes, which one to use when? the difference is: 
in the first query you are returning only the Employes for the Hibernate. In the second query, you are returning the Employes and all Departments associated. 
If you don't use  fetch  and the Departments continue to be returned, is because your mapping between Employee and Department (a  @OneToMany ) are setted with  FetchType.EAGER . In this case, any HQL (with  fetch  or not) query with  FROM Employee  will bring all Departments. Remember that all mapping *ToOne ( @ManyToOne  and  @OneToOne ) are EAGER by default. 
原文を参照:http://zccbbg.top/2017/05/31/difference-join-join-fetch-jpa/