oracle外键属性

外键的属性

[ ON  DELETE CASCADE | SET NULL ] [ [[NOT] DEFERRABLE] [INITIALLY { IMMEDIATE | DEFERRED }]

| [INITIALLY { IMMEDIATE | DEFERRED }] [[NOT] DEFERRABLE]]

[ RELY | NORELY ] [using_index_clause] [ ENABLE | DISABLE ]

[ VALIDATE | NOVALIDATE ] [exceptions_clause]

1,[ENABLE | DISABLE] [ VALIDATE | NOVALIDATE ]

前边代表：启用 (ENABLE) 或禁用 (DISABLE) 完整性约束条件

后边代表：VALIDATE/NOVALIDATE 针对已有数据的完整性约束检查

2，[ [[NOT] DEFERRABLE] [INITIALLY { IMMEDIATE | DEFERRED }]

immediate:在执行语句时检查约束

deferred:提交事务时检查约束

在执行数据导入时候特别有用

3，[ ON  DELETE CASCADE | SET NULL ]

在删除主表时候的处理方式