Question

When I try to delete a “Course” object, I get this exception:
Referential integrity constraint violation: "FKCE6C075833B16F41: PUBLIC.TEACHER_COURSE FOREIGN KEY(COURSES_ID) REFERENCES PUBLIC.COURSE(ID)" SQL statement: delete from Course where id=?

The “Course” class looks like this:

@Entity
public class Course extends Model {
  @ManyToOne
  public Teacher teacher;
  ...
}

The “Teacher” class looks like this:

@Entity
public class Teacher extends Model {
  @OneToMany(mappedBy="teacher", cascade=CascadeType.ALL)
  public List<Course> courses;
  ...
}

Whenever I try to delete a “Course” from my controller (using the delete() method), I get the exception above. How do I fix it? I’ve tried various ways of mapping. Do I need to fix the schema of the database somewhere?

Thanks for all the help! This is my first post here, if there’s anything I need to make clearer, please let me know!

Answer 1

Looks to me like you’re trying to delete a Course record, but there is still a Teacher record that has a reference to the course you’re trying to delete (stored in the TEACHER_COURSE join table). This is normal, because you have defined a bi-directional relationship: a Course knows its Teacher, and a Teacher knows the Course objects that belong to it.

One option would be to simply get rid of the bi-directional relationship if possible (eg. remove the relationship from Teacher to Course by remove the courses list). Another would be to remove the Course instance you want to delete from the courses list first, and then delete it (note: you may have to persist/merge the courses list first before deleting the course so there is no link anymore).

This question on the matter may provide some additional insight.