mysql> CREATE TABLE `roottb` (
-> `id` INT(11) UNSIGNED AUTO_INCREMENT NOT NULL,
-> `data` VARCHAR(100) NOT NULL DEFAULT '',
-> PRIMARY KEY (`id`)
-> ) engine=InnoDB;
Query OK, 0 rows affected (0.60 sec)
mysql> CREATE TABLE `subtb` (
-> `id` INT(11) UNSIGNED AUTO_INCREMENT NOT NULL,
-> `rootid` INT(11) UNSIGNED NOT NULL DEFAULT '0',
-> `data` VARCHAR(100) NOT NULL DEFAULT '',
-> PRIMARY KEY (`id`),
-> INDEX (`rootid`),
-> FOREIGN KEY (`rootid`) REFERENCES roottb(`id`) ON DELETE CASCADE
-> ) engine=InnoDB;
Query OK, 0 rows affected (0.16 sec)
mysql> INSERT INTO `roottb` (`id`,`data`)
-> VALUES ('1', 'test root line 1'),
-> ('2', 'test root line 2'),
-> ('3', 'test root line 3');
Query OK, 3 rows affected (0.08 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql>
mysql> INSERT INTO `subtb` (`id`,`rootid`,`data`)
-> VALUES ('1', '1', 'test sub line 1 for root 1'),
-> ('2', '1', 'test sub line 2 for root 1'),
-> ('3', '1', 'test sub line 3 for root 1'),
-> ('4', '2', 'test sub line 1 for root 2'),
-> ('5', '2', 'test sub line 2 for root 2'),
-> ('6', '2', 'test sub line 3 for root 2'),
-> ('7', '3', 'test sub line 1 for root 3'),
-> ('8', '3', 'test sub line 2 for root 3'),
-> ('9', '3', 'test sub line 3 for root 3');
Query OK, 9 rows affected (0.14 sec)
Records: 9 Duplicates: 0 Warnings: 0
mysql> delete from `roottb` where `id`='2';
Query OK, 1 row affected (0.16 sec)
mysql> select * from `roottb`;
+----+------------------+
| id | data |
+----+------------------+
| 1 | test root line 1 |
| 3 | test root line 3 |
+----+------------------+
2 rows in set (0.02 sec)
mysql> select * from `subtb`;
+----+--------+----------------------------+
| id | rootid | data |
+----+--------+----------------------------+
| 1 | 1 | test sub line 1 for root 1 |
| 2 | 1 | test sub line 2 for root 1 |
| 3 | 1 | test sub line 3 for root 1 |
| 7 | 3 | test sub line 1 for root 3 |
| 8 | 3 | test sub line 2 for root 3 |
| 9 | 3 | test sub line 3 for root 3 |
+----+--------+----------------------------+
6 rows in set (0.00 sec)