给定3个表:
student (id)
student_to_class (student_id, class_id)
class (id)
我想在student_to_class上应用where子句,其中student_id =:studentId。我发现许多示例都适用“ class”表或“ student”表上的where子句,但不适用于多对多表。
学生表有一个@ManyToMany
@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(
name = "student_to_class",
joinColumns = { @JoinColumn(name = "student_id", nullable = false) },
inverseJoinColumns = { @JoinColumn(name = "class_id", nullable = false) }
)
private Set<ClassEntity> classes;
类表中有一个@ManyToMany
@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(
name = "student_to_class",
joinColumns = { @JoinColumn(name = "class_id", nullable = false) },
inverseJoinColumns = { @JoinColumn(name = "student_id", nullable = false) }
)
private Set<StudentEntity> students;
这是我要转换为条件的查询:
select * from student, student_to_class where student_to_class.student_id = 1 and student.id = student_to_class.class_id
我试图弄清楚如何引用多对多表,因为我没有代表该表的实际类。
Criteria c = sessionFactory.getCurrentSession().createCriteria(ClassEntity.class);
c.createAlias("student_to_class", "entities"); // how to reference the student_to_class ?
c.add(Restrictions.eq("entities.user_id", studentEntity.getId()));
但是我遇到了一个错误,这对我来说很有意义,但是我没有很多运气来修复它:
无法解析属性:student_to_class
最佳答案
由于Student表中的studentid
与studentid
表中的student_to_class
相同,因此无需按联接表进行过滤。只需对student.student_id
运行where子句
关于java - 多对多where子句,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/14679039/