ON DELETE CASCADE not working in MySQL

I am using the following SQL to create a table named app_info:

CREATE TABLE IF NOT EXISTS `app_info` (
`_id` int(11) NOT NULL AUTO_INCREMENT,
`app_name` varchar(50) DEFAULT NULL,
`app_owner` varchar(50) DEFAULT NULL,
`last_update` timestamp NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
PRIMARY KEY (`_id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=6 ;

I am using the following SQL to create a table named tab_info:

CREATE  TABLE `myDB`.`tab_info` (
`_id` INT NOT NULL AUTO_INCREMENT ,
`app_id` INT NOT NULL ,
`tab_title` VARCHAR(15) NOT NULL ,
PRI开发者_运维百科MARY KEY (`_id`) ,
UNIQUE INDEX `app_id_UNIQUE` (`app_id` ASC) ,
INDEX `app_tab_key` (`app_id` ASC) ,
CONSTRAINT `app_tab_key`
  FOREIGN KEY (`app_id` )
  REFERENCES `myDB`.`app_info` (`_id` )
  ON DELETE CASCADE
  ON UPDATE CASCADE); 

But when I delete data from primary key table, the orphaned rows in the foreign key table are not being deleted automatically. Does anyone know what the problem could be?

The MyISAM storage engine doesn't support foreign key constraints. The constraint is parsed but silently ignored.

To fix your problem use the InnoDB engine instead (for both tables).

CREATE TABLE ( ... ) ENGINE = InnoDB ... ;

Instead of dropping your tables and recreating them you can also change the storage engine:

ALTER TABLE myDB.app_info ENGINE = InnoDB;
ALTER TABLE myDB.tab_info ENGINE = InnoDB;

After changing the engine you will need to add the foreign key constraint again.