Question

有人能告诉我为什么会收到此错误消息吗？当我尝试创建RENTAL表时，会弹出错误。

CREATE TABLE CAR_CLASS
(CAR_CLASS_ID INT(3) PRIMARY KEY,
CAR_CLASS CHAR(20),
RENTAL_RATE DECIMAL(4,2) );

CREATE TABLE CAR
(CAR_ID CHAR(25) PRIMARY KEY,
CAR_CLASS_ID INT(3),
CAR_COLOR CHAR(20),
FOREIGN KEY (CAR_CLASS_ID) REFERENCES CAR_CLASS(CAR_CLASS_ID) );

CREATE TABLE CUSTOMER_INFO
(CUSTOMER_ID CHAR(30) PRIMARY KEY,
CUSTOMER_FIRST CHAR(30),
CUSTOMER_LAST CHAR(30),
CUSTOMER_CC_NUMBER CHAR(16));


CREATE TABLE RENTAL
(RENTAL_ID INT(3) PRIMARY KEY,
RENTAL_DATE_OUT DATE,
RENTAL_DATE_IN DATE,
CAR_CLASS_ID INT(3),
CAR_ID CHAR(25),
CUSTOMER_ID CHAR(30),
FOREIGN KEY (CAR_CLASS_ID) REFERENCES CAR_CLASS(CAR_CLASS_ID),
FOREIGN KEY (CAR_ID) REFERENCES CAR(CAR_ID),
FOREIGN KEY (CUSTOMER_ID) REFERENCES CUSTOMER(CUSTOMER_ID) );

Answer 1

您的其他表名为CUSTOMER_INFO，而您的外键仅引用CUSTOMER。将上一个CREATE TABLE更改为：

CREATE TABLE RENTAL
(RENTAL_ID INT(3) PRIMARY KEY,
RENTAL_DATE_OUT DATE,
RENTAL_DATE_IN DATE,
CAR_CLASS_ID INT(3),
CAR_ID CHAR(25),
CUSTOMER_ID CHAR(30),
FOREIGN KEY (CAR_CLASS_ID) REFERENCES CAR_CLASS(CAR_CLASS_ID),
FOREIGN KEY (CAR_ID) REFERENCES CAR(CAR_ID),
FOREIGN KEY (CUSTOMER_ID) REFERENCES CUSTOMER_INFO(CUSTOMER_ID) );

Answer 2

创建RENTAL表时表的名称是错误的。

查看代码的最后一行。

FOREIGN KEY（CUSTOMER_ID）引用CUSTOMER（CUSTOMER_ID）。

而不是客户，应该是CUSTOMER_INFO。

一切顺利：）

错误代码：1215。无法添加外键约束

2 个答案: