我无法删除记录“无法删除或更新父行：外键约束失败。我该如何解决这个问题？

Question

我试图删除评级表中的记录，然后

无法添加或更新子行：外键约束失败（ fyprojectdb . ratings , CONSTRAINT FKdyash6f91887unaan9mj9b460 FOREIGN KEY ( answer_id ) REFERENCES answers ( answer_id )）

发生此错误。 如何修复此错误。 我已经正确映射了两个实体。

@Entity
@Table(name = "ratings")
public class Ratings {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long rating_id;

    @Column(nullable = false, unique = false, length = 45)
    private Short ratingValue;

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "userId")
    private User user;

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "answer_id")
    private Answer answer;

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "question_id")
    private Question question;
//getters and setters

@Entity
@Table(name = "answers")
public class Answer {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long answer_id;

    @Column(nullable = false, unique = false, length = 100)
    private String fullAnswer;

    /*Many to one mapping question*/
    @ManyToOne(cascade = CascadeType.REMOVE)
    @JoinColumn(name = "question_id")
    private Question question;

    /* Many to One mapping with users*/
    @ManyToOne(cascade = CascadeType.REMOVE)
    @JoinColumn(name = "userId")
    private User user;
//getters and setters

Answer 1

原因是这里的cascade = CascadeType.ALL

@ManyToOne(cascade = CascadeType.ALL)
@JoinColumn(name = "userId")
private User user;

这意味着在删除任何Ratings后必须删除User 。

最好使用RatingEntity作为实体，使用RATINGS作为表名。

一般规则

切勿将任何cascade与关联的@ManyToOne部分一起使用！

还要始终将fetch = FetchType.LAZY与@ManyToOne一起使用。

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "userId")
    private User user;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "answer_id")
    private Answer answer;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "question_id")
    private Question question;