外键和MySQL错误

Question

我有以下脚本在MySQL版本5.1中创建一个表来引用其他3个表。所有3个表都是使用InnoDB创建的，并且所有3个表都将ID列定义为INT。

我已经成功创建了其他表，引用了ACCOUNT和PERSON，但是，这是第一个引用ADDRESS的表，所以我在下面也包含了该表的定义，如下所示。

我得到的错误是ERROR 1005（HY000）与errno 150，我理解这与外键创建有关。

失败的脚本是（为简单起见，删除了额外的列）：

CREATE TABLE WORK_ORDER (
    ID INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    ACCOUNT_ID INT NOT NULL,
    CUSTOMER_ID INT NOT NULL,
    SALES_ID INT,
    TRADES_ID INT,
    LOCATION_ID INT NOT NULL,
    INDEX CUST_INDEX(CUSTOMER_ID),
    INDEX SALES_INDEX(SALES_ID),
    INDEX TRADES_INDEX(TRADES_ID),
    INDEX ACCOUNT_INDEX(ACCOUNT_ID),
    INDEX LOCATION_INDEX(LOCATION_ID),
    FOREIGN KEY (CUSTOMER_ID) REFERENCES PERSON(ID) ON DELETE CASCADE,
    FOREIGN KEY (SALES_ID) REFERENCES PERSON(ID) ON DELETE SET NULL,
    FOREIGN KEY (TRADES_ID) REFERENCES PERSON(ID) ON DELETE SET NULL,
    FOREIGN KEY (ACCOUNT_ID) REFERENCES ACCOUNT(ID) ON DELETE CASCADE,
    FOREIGN KEY (LOCATION_ID) REFERENCES ADDRESS(ID) ON DELETE SET NULL
) ENGINE=InnoDB;

用于创建ADDRESS表的SQL语句如下（为简单起见，删除了额外的列）。

CREATE TABLE ADDRESS (
    ID INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    PERSON_ID INT NOT NULL,
    ACCOUNT_ID INT NOT NULL,
    ADDRESS_L1 VARCHAR(50),
    ADDRESS_L2 VARCHAR(50),
    CITY VARCHAR(25),
    PROVINCE VARCHAR(20),
    POSTAL_CODE VARCHAR(6),
    COUNTRY VARCHAR(25),
    INDEX CUST_INDEX(PERSON_ID),
    INDEX ACCOUNT_INDEX(ACCOUNT_ID),
    FOREIGN KEY (ACCOUNT_ID) REFERENCES ACCOUNT(ID) ON DELETE CASCADE,
    FOREIGN KEY (PERSON_ID) REFERENCES PERSON(ID) ON DELETE CASCADE
) ENGINE=InnoDB;

我在这里浏览了几个处理类似问题的问题，但大多数似乎是重复定义和不匹配字段类型，以及一些不使用InnoDB用于其中一个或另一个表。但是，这些似乎都不是问题所在。有什么想法吗？

Answer 1

您始终可以发出'SHOW ENGINE INNODB STATUS'命令。埋在输出中的将是“最新的外键错误”。部分，将详细说明导致'150'错误的原因：

mysql> create table a (x int not null) type=innodb;
Query OK, 0 rows affected, 1 warning (0.02 sec)

mysql> create table b (y int not null, foreign key (y) references a (x) on delete set null) type=innodb;
ERROR 1005 (HY000): Can't create table './test/b.frm' (errno: 150)

mysql> show engine innodb status;
[..... snip snip snip ...]
------------------------
LATEST FOREIGN KEY ERROR
------------------------
091129 16:32:41 Error in foreign key constraint of table test/b:
foreign key (y) references a (x) on delete set null) type=innodb:
You have defined a SET NULL condition though some of the
columns are defined as NOT NULL.
[.... snip snip snip ...]