How to solve the problem of failed creation of mysql foreign keys
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Create a persons:
CREATE TABLE `persons` (
`id_ p` int (11) NOT NULL AUTO_INCREMENT
`lastname` varchar (10) DEFAULT NULL
`firstname` varchar (10) DEFAULT NULL
`address` varchar (50) DEFAULT NULL
`city` varchar (10) DEFAULT NULL
PRIMARY KEY (`id_ p`)
); www.2cto.com
Re-create table orders:
CREATE TABLE `orders` (
`id_ o` int (11) NOT NULL AUTO_INCREMENT
`orderno` int (11) NOT NULL
`id_ p` int (11) NOT NULL
PRIMARY KEY (`id_ o`)
FOREIGN KEY (`id_ p`) REFERENCES `persons` (`id_ p`)
);
Using the show create table orders statement to query the information of orders, it is found that the foreign key was not created successfully. After checking some information, we finally found out the reason. The table created by mysql by default is of type MyISAM, and the type of the table needs to be specified as innodb:
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CREATE TABLE `orders` (
`id_ o` int (11) NOT NULL AUTO_INCREMENT
`orderno` int (11) NOT NULL
`id_ p` int (11) NOT NULL
PRIMARY KEY (`id_ o`)
FOREIGN KEY (`id_ p`) REFERENCES `persons` (`id_ p`)
) ENGINE=InnoDB
However, the following error is prompted at this time:
ERROR 1005 (HY000): Can't create table 'test.orders' (errno: 150)
It is OK to specify the type of persons table as innodb.
Summarize several situations in which foreign key creation failed:
1. Foreign keys are different from referenced foreign keys, such as integer and double
two。 Could not find the column to be referenced
3. The character encoding of the table is different.
4. Data engine types are inconsistent, such as innodb and myisam
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