Query for getting data not attached to a particular variable - JPA

Question

I have a table of Employee's and a Meeting variable (also I have a table for Meeting). The relationship beetween Meeting and Employee is many-to-many. Is it possible to write a JPA Query which gets all the Employees from the database which are attached to the Meeting variable. If so what is the query ? The other option is to get all Employees and see which ones are not in the Meeting variable, but maybe is slow. Any ideas what should I do ?

Answer 1

For example this is your Employee entity:

@Entity
public class Employee  {

    @ManyToMany(mappedBy="employee")
    private List<Meeting> meetings;
    ...
}

Query: Get all the Employees from the database which are attached to the Meeting variable

SELECT e FROM Employee e WHERE :meeting MEMBER OF e.meetings

Query: Get all Employees and see which ones are not in the Meeting variable

SELECT e FROM Employee e WHERE :meeting NOT MEMBER OF e.meetings

Sample code:

String query = "SELECT e FROM Employee e WHERE :meeting MEMBER OF e.meetings";

Meeting meeting = new Meeting();
meeting.setId(1);

TypedQuery<Employee> query = em.createQuery(query, Employee.class);
List<Employee> employeesInMeeting = query.setParameter("meeting", meeting).getResultList();  
// this will select all employees that has a meeting with id=1 in their list