用于检查集合大小是否为0或空的HQL查询

使用 IS EMPTY 应该有效(我更喜欢JPQL语法):

SELECT u FROM User u WHERE u.status = 1 AND u.appointments IS EMPTY

如果没有,请显示生成的SQL。

工具书类

• 休眠核心参考指南
  • 14.10. Expressions
• JPA 1.0规范
  • 第4.6.11节“空集合比较表达式”

您是否查看了生成的SQL?你的方法在这里很有效:

// Hibernate query:
const string hql = "from User u where u.Id = 101 and size(u.Appointments) = 0";


// Generates this working SQL:
select user0_.Id    as Id20_,
       user0_.Name as Name2_20_
from   User user0_
where  user0_.Id = 101
       and (select count(appointment1_.Id_Solicitud)
            from   Appointment appointment1_
            where  user0_.Id = appointment1_.Id_User) = 0

// Hibernate query:
const string hql = "from User u where u.Id = 101 and size(u.Appointments) = 0";