4

简单的 JPA/JPQL 问题。我有一个具有多对多关系的实体:

@Entity
public class Employee {      
  @ManyToMany
  @JoinTablename="employee_project"
      joinColumns={@JoinColumn(name="employee_id"}
      inverseJoinColumns={@JoinColumn(name="project_id"})
  private List<Project> projects;

返回所有没有任何项目的员工的 JPQL 查询是什么?

4

2 回答 2

6
from Employee e where not exists elements(e.projects)

或者

from Employee e where size(e.projects) = 0
于 2009-10-06T21:41:45.163 回答
4

JQPL 确实有专门IS [NOT] EMPTY的比较运算符来检查集合是否为空:

SELECT e FROM Employee e WHERE e.projects IS EMPTY
于 2012-08-29T04:56:25.683 回答