我想要与 Symfony 和 Doctrine 建立简单的多对多关系。这实际上是一个单向的一对多关联，可以通过连接表映射为文档表明 http://doctrine-orm.readthedocs.org/en/latest/reference/association-mapping.html#one-to-many-unidirectional-with-join-table我使用 YAML 文件通过以下代码进行配置：
在文件 Content.orm.yml 中：
manyToMany:
comments:
cascade: ["persist","remove"]
onDelete: CASCADE
options:
cascade:
remove: true
persist: true
#refresh: true
#merge: true
#detach: true
orphanRemoval: false
orderBy: null
targetEntity: Comment
joinTable:
name: content_comments
joinColumns:
content_id:
referencedColumnName: id
inverseJoinColumns:
comment_id:
referencedColumnName: id
unique: true
这会产生以下 SQL 命令：
$ php app/console doctrine:schema:update --dump-sql | grep -i "comment\|content"
CREATE TABLE comment (id INT AUTO_INCREMENT NOT NULL, text LONGTEXT NOT NULL, content_id INT NOT NULL, creation_date DATETIME NOT NULL, PRIMARY KEY(id)) DEFAULT CHARACTER SET utf8 COLLATE utf8_unicode_ci ENGINE = InnoDB;
CREATE TABLE contents (id INT AUTO_INCREMENT NOT NULL, user INT DEFAULT NULL, user_id INT NOT NULL,file VARCHAR(255) DEFAULT NULL, INDEX IDX_B4FA11778D93D649 (user), PRIMARY KEY(id)) DEFAULT CHARACTER SET utf8 COLLATE utf8_unicode_ci ENGINE = InnoDB;
CREATE TABLE content_comments (content_id INT NOT NULL, comment_id INT NOT NULL, INDEX IDX_D297CC584A0A3ED (content_id), UNIQUE INDEX UNIQ_D297CC5F8697D13 (comment_id), PRIMARY KEY(content_id, comment_id)) DEFAULT CHARACTER SET utf8 COLLATE utf8_unicode_ci ENGINE = InnoDB;
ALTER TABLE contents ADD CONSTRAINT FK_B4FA11778D93D649 FOREIGN KEY (user) REFERENCES users (id);
ALTER TABLE content_comments ADD CONSTRAINT FK_D297CC584A0A3ED FOREIGN KEY (content_id) REFERENCES contents (id);
ALTER TABLE content_comments ADD CONSTRAINT FK_D297CC5F8697D13 FOREIGN KEY (comment_id) REFERENCES comment (id);
但正如您所看到的，即使我尝试放置我找到的所有 YAML 注释，FOREIGN KEY 指令也没有“ON DELETE CASCADE”部分。
因为在代码中，我试图删除一个“内容”实体以及与此代码关联的所有“注释”：
$comments = $content->getComments();
// Remove first the parent
$entity_manager->remove($content);
$entity_manager->flush();
// Remove the childs
foreach($comments as $comment)
{
$entity_manager->remove($comment);
}
$entity_manager->flush();
这会产生以下异常。
An exception occurred while executing 'DELETE FROM comment WHERE id = ?' with params [1]:\n\nSQLSTATE[23000]: Integrity constraint violation: 1451 Cannot delete or update a parent row: a foreign key constraint fails (`bb2server`.`content_comments`, CONSTRAINT `FK_D297CC5F8697D13` FOREIGN KEY (`comment_id`) REFERENCES `comment` (`id`))
那么，我做错了什么？或者如何强制 Doctrine 在多对多关系中放置“ON DELETE CASCADE”？
我唯一肮脏的解决方法是删除 SQL 查询并自行重建，但我需要 Doctrine 在 schema:update 中创建查询以避免我修补：
mysql> show create table content_comments;
+------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| content_comments | CREATE TABLE `content_comments` (
`content_id` int(11) NOT NULL,
`comment_id` int(11) NOT NULL,
PRIMARY KEY (`content_id`,`comment_id`),
UNIQUE KEY `UNIQ_D297CC5F8697D13` (`comment_id`),
KEY `IDX_D297CC584A0A3ED` (`content_id`),
CONSTRAINT `FK_D297CC584A0A3ED` FOREIGN KEY (`content_id`) REFERENCES `contents` (`id`),
CONSTRAINT `FK_D297CC5F8697D13` FOREIGN KEY (`comment_id`) REFERENCES `comment` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci |
+------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql> ALTER TABLE content_comments DROP FOREIGN KEY FK_D297CC5F8697D13;
Query OK, 0 rows affected (0.04 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> ALTER TABLE content_comments ADD CONSTRAINT FK_D297CC5F8697D13 FOREIGN KEY (`content_id`) REFERENCES `contents` (`id`) ON DELETE CASCADE;
Query OK, 10 rows affected (0.07 sec)
Records: 10 Duplicates: 0 Warnings: 0
编辑：解决方法。我需要将 onDelete: CASCADE 放在 JoinColumns 下
manyToMany:
comments:
cascade: ["persist","remove"]
onDelete: CASCADE
options:
cascade:
remove: true
persist: true
#refresh: true
#merge: true
#detach: true
orphanRemoval: false
orderBy: null
targetEntity: Comment
joinTable:
name: content_comments
joinColumns:
content_id:
referencedColumnName: id
onDelete: CASCADE
inverseJoinColumns:
comment_id:
referencedColumnName: id
unique: true
onDelete: CASCADE
