MYSQL CASCADE DELETE 引发的思考

MYSQL CASCADE DELETE ：级联删除。这个概念还是学习Oracle时得到的。

就是主键记录删除时，相关的有外键的表里的记录，也删除。

https://dev.mysql.com/doc/refman/5.7/en/delete.html

https://stackoverflow.com/questions/2914936/mysql-foreign-key-constraints-cascade-delete

http://www.mysqltutorial.org/mysql-on-delete-cascade/

上面三个帖子解释的比较清楚。

另外CASCADE模式需要MYSQL引擎支持：Engine必须是InnoDB。

mysql> SHOW ENGINES;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine             | Support | Comment                                                        | Transactions | XA   | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| PERFORMANCE_SCHEMA | YES     | Performance Schema                                             | NO           | NO   | NO         |
| CSV                | YES     | CSV storage engine                                             | NO           | NO   | NO         |
| MRG_MYISAM         | YES     | Collection of identical MyISAM tables                          | NO           | NO   | NO         |
| BLACKHOLE          | YES     | /dev/null storage engine (anything you write to it disappears) | NO           | NO   | NO         |
| MyISAM             | YES     | MyISAM storage engine                                          | NO           | NO   | NO         |
| MEMORY             | YES     | Hash based, stored in memory, useful for temporary tables      | NO           | NO   | NO         |
| ARCHIVE            | YES     | Archive storage engine                                         | NO           | NO   | NO         |
| InnoDB             | DEFAULT | Supports transactions, row-level locking, and foreign keys     | YES          | YES  | YES        |
| FEDERATED          | NO      | Federated MySQL storage engine                                 | NULL         | NULL | NULL       |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
9 rows in set

mysql> 

一篇比较常用的两个引擎MyISAM和InnoDB的文章：

http://www.oschina.net/question/17_4248