(`library`.`book_loans`，约束`book_loans_ibfk_3`外键(“`isbn`”)引用“`book`”(“isbn”))

Question

java.sql.SQLIntegrityConstraintViolationException:无法添加或更新子行:外键约束失败(library.book_loans、约束book_loans_ibfk_3外键(isbn)引用book (isbn))

这是我的表代码

book_loans \x{e76f}

CREATE TABLE `book_loans` (
    `loan_id` int(11) NOT NULL,
    `isbn` varchar(10) DEFAULT NULL,
    `Card_ID` mediumint(9) NOT NULL AUTO_INCREMENT,
    `date_out` date DEFAULT NULL,
    `due_date` date DEFAULT NULL,
    `date_in` date DEFAULT NULL,
    PRIMARY KEY (`loan_id`),
    KEY `book_loans_ibfk_2` (`Card_ID`),
    KEY `isbn` (`isbn`),
    CONSTRAINT `book_loans_ibfk_2` FOREIGN KEY (`Card_ID`) 
        REFERENCES `borrower` (`Card_ID`),
    CONSTRAINT `book_loans_ibfk_3` FOREIGN KEY (`isbn`) 
        REFERENCES `book` (`isbn`)
) ENGINE=InnoDB 
    AUTO_INCREMENT=1002 
    DEFAULT CHARSET=utf8mb4 
    COLLATE=utf8mb4_0900_ai_ci

图书\x{e76f}

CREATE TABLE `book` (
    `isbn` varchar(10) NOT NULL,
    `title` varchar(500) DEFAULT NULL,
    PRIMARY KEY (`isbn`)
) ENGINE=InnoDB 
    DEFAULT CHARSET=utf8mb4 
    COLLATE=utf8mb4_0900_ai_ci

借款人

CREATE TABLE `borrower` (
    `Card_ID` mediumint(9) NOT NULL AUTO_INCREMENT,
    `Ssn` varchar(11) DEFAULT NULL,
    `Bname` varchar(50) DEFAULT NULL,
    `Address` varchar(100) DEFAULT NULL,
    `Phone` varchar(15) DEFAULT NULL,
    PRIMARY KEY (`Card_ID`),
    UNIQUE KEY `Ssn` (`Ssn`)
) ENGINE=InnoDB 
    AUTO_INCREMENT=1002 
    DEFAULT CHARSET=utf8mb4 
    COLLATE=utf8mb4_0900_ai_ci

Answer 1

当您为"book_loans“表的"isbn”属性插入一个未包含在主键值集中的值时，可能会出现此异常。