在MySQL中从多对多关系中删除 [英] Delete from Many to Many Relationship in MySQL

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问题描述

我不是MySQL专业人员，我只是想制作一个简单的Java应用程序，该应用程序可以访问MySQL数据库(例如著名的图书/作者数据库)并进行操作(即添加，更新，删除).

问题是，当我尝试使用

删除时，有两个表具有多对多关系(例如authors表和books表) 

DELETE FROM tableName WHERE someColumnName = 'someValue'

它会引发MySQLIntegrityConstraintViolationException，并显示消息无法删除或更新父行:外键约束失败"

我知道这是由于多对多"的关系，但是实际上我不知道该怎么办，因为我不是MySQL专业人员.任何帮助将不胜感激.谢谢.

修改: 这是数据库

DROP DATABASE IF EXISTS books;

CREATE DATABASE books;

USE books;

CREATE TABLE Authors
(
   AuthorID int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   FirstName varchar(30) NOT NULL,
   LastName varchar(30) NOT NULL
)                 ;
CREATE TABLE Titles
(
   ISBN varchar(20) NOT NULL PRIMARY KEY,
   Title varchar(100) NOT NULL,
   EditionNumber int NOT NULL,
   Copyright varchar(4) NOT NULL
)             ;

CREATE TABLE AuthorISBN
(
   AuthorID int NOT NULL,
   ISBN varchar(20) NOT NULL,
   FOREIGN KEY (AuthorID) REFERENCES Authors(AuthorID) ON DELETE SET NULL,
   FOREIGN KEY (ISBN) References Titles(ISBN) ON DELETE SET NULL
)            ;

INSERT INTO Authors (FirstName,LastName) VALUES ('Paul','Deitel')           ;
INSERT INTO Authors (FirstName,LastName) VALUES ('Harvey','Deitel')     ;
INSERT INTO Authors (FirstName,LastName) VALUES ('Abbey','Deitel')     ;
INSERT INTO Authors (FirstName,LastName) VALUES ('Michael','Morgano')    ;
INSERT INTO Authors (FirstName,LastName) VALUES ('Eric','Kern')     ;


INSERT INTO Titles (ISBN,Title,EditionNumber,Copyright) VALUES ('0132152134','Visual Basic 2010 How to Program',5,'2011')          ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (1,'0132152134')     ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (2,'0132152134') ;

INSERT INTO Titles (ISBN,Title,EditionNumber,Copyright) VALUES ('0132151421','Visual C# 2010 How to Program',4,'2011')  ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (1,'0132151421')      ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (2,'0132151421')      ;

INSERT INTO Titles (ISBN,Title,EditionNumber,Copyright) VALUES ('0132575663','Java How to Program',9,'2012')   ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (1,'0132575663')                                               ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (2,'0132575663')                                       ;

INSERT INTO Titles (ISBN,Title,EditionNumber,Copyright) VALUES ('0132662361','C++ How to Program',8,'2012')     ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (1,'0132662361')                                                  ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (2,'0132662361')                                                 ;

INSERT INTO Titles (ISBN,Title,EditionNumber,Copyright) VALUES ('0132404168','C How to Program',6,'2010')     ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (1,'0132404168')                                             ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (2,'0132404168')                                       ;

INSERT INTO Titles (ISBN,Title,EditionNumber,Copyright) VALUES ('013705842X','iPhone for Programmers: An App-Driven Approach',1,'2010')        ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (1,'013705842X')                                                    ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (2,'013705842X')                                                    ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (3,'013705842X')                                                    ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (4,'013705842X')                                                    ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (5,'013705842X')                                                    ;

INSERT INTO Titles (ISBN,Title,EditionNumber,Copyright) VALUES ('0132121360','Android for Programmers: An App-Driven Approach',1,'2012')        ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (1,'0132121360')                                                    ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (2,'0132121360')                                                    ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (3,'0132121360')                                                    ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (4,'0132121360')                                                    ;

解决方案

通过在两个 FOREIGN KEY 语句之后删除NOT NULL单词并添加ON DELETE CASCADE和ON UPDATE CASCADE来解决此问题. /p>

I am not a MySQL professional I am just trying to make simple java application which accesses a MySQL database (e.g. The famous books/authors database) and manipulates it (i.e, add, update, delete).

The problem is that there are two tables that have many to many relationship (e.g. authors table and books table) when I am trying to delete using 

DELETE FROM tableName WHERE someColumnName = 'someValue'

it throws MySQLIntegrityConstraintViolationException with the message "Cannot delete or update a parent row: a foreign key constraint fails"

I know it's because of the "many to many" relationship but actually I don't know what to do with this since I am not a MySQL professional. Any help will be appreciated. Thank you.

Edit: here's the database

DROP DATABASE IF EXISTS books;

CREATE DATABASE books;

USE books;

CREATE TABLE Authors
(
   AuthorID int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   FirstName varchar(30) NOT NULL,
   LastName varchar(30) NOT NULL
)                 ;
CREATE TABLE Titles
(
   ISBN varchar(20) NOT NULL PRIMARY KEY,
   Title varchar(100) NOT NULL,
   EditionNumber int NOT NULL,
   Copyright varchar(4) NOT NULL
)             ;

CREATE TABLE AuthorISBN
(
   AuthorID int NOT NULL,
   ISBN varchar(20) NOT NULL,
   FOREIGN KEY (AuthorID) REFERENCES Authors(AuthorID) ON DELETE SET NULL,
   FOREIGN KEY (ISBN) References Titles(ISBN) ON DELETE SET NULL
)            ;

INSERT INTO Authors (FirstName,LastName) VALUES ('Paul','Deitel')           ;
INSERT INTO Authors (FirstName,LastName) VALUES ('Harvey','Deitel')     ;
INSERT INTO Authors (FirstName,LastName) VALUES ('Abbey','Deitel')     ;
INSERT INTO Authors (FirstName,LastName) VALUES ('Michael','Morgano')    ;
INSERT INTO Authors (FirstName,LastName) VALUES ('Eric','Kern')     ;


INSERT INTO Titles (ISBN,Title,EditionNumber,Copyright) VALUES ('0132152134','Visual Basic 2010 How to Program',5,'2011')          ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (1,'0132152134')     ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (2,'0132152134') ;

INSERT INTO Titles (ISBN,Title,EditionNumber,Copyright) VALUES ('0132151421','Visual C# 2010 How to Program',4,'2011')  ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (1,'0132151421')      ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (2,'0132151421')      ;

INSERT INTO Titles (ISBN,Title,EditionNumber,Copyright) VALUES ('0132575663','Java How to Program',9,'2012')   ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (1,'0132575663')                                               ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (2,'0132575663')                                       ;

INSERT INTO Titles (ISBN,Title,EditionNumber,Copyright) VALUES ('0132662361','C++ How to Program',8,'2012')     ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (1,'0132662361')                                                  ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (2,'0132662361')                                                 ;

INSERT INTO Titles (ISBN,Title,EditionNumber,Copyright) VALUES ('0132404168','C How to Program',6,'2010')     ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (1,'0132404168')                                             ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (2,'0132404168')                                       ;

INSERT INTO Titles (ISBN,Title,EditionNumber,Copyright) VALUES ('013705842X','iPhone for Programmers: An App-Driven Approach',1,'2010')        ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (1,'013705842X')                                                    ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (2,'013705842X')                                                    ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (3,'013705842X')                                                    ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (4,'013705842X')                                                    ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (5,'013705842X')                                                    ;

INSERT INTO Titles (ISBN,Title,EditionNumber,Copyright) VALUES ('0132121360','Android for Programmers: An App-Driven Approach',1,'2012')        ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (1,'0132121360')                                                    ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (2,'0132121360')                                                    ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (3,'0132121360')                                                    ;
INSERT INTO AuthorISBN (AuthorID,ISBN) VALUES (4,'0132121360')                                                    ;

解决方案

Fixed the problem by removing the NOT NULL words and adding ON DELETE CASCADE and ON UPDATE CASCADE after both FOREIGN KEY statements.

这篇关于在MySQL中从多对多关系中删除的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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