我無法刪除記錄“無法刪除或更新父行：外鍵約束失敗。我該如何解決這個問題？

Question

我試圖刪除評級表中的記錄，然后

無法添加或更新子行：外鍵約束失敗（ fyprojectdb . ratings , CONSTRAINT FKdyash6f91887unaan9mj9b460 FOREIGN KEY ( answer_id ) REFERENCES answers ( answer_id )）

發生此錯誤。 如何修復此錯誤。 我已經正確映射了兩個實體。

@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

原因是這里的cascade = CascadeType.ALL

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

這意味着在刪除任何Ratings后必須刪除User 。

最好使用RatingEntity作為實體，使用RATINGS作為表名。

一般規則

切勿將任何cascade與關聯的@ManyToOne部分一起使用！

還要始終將fetch = FetchType.LAZY與@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;