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HomeDatabaseMysql TutorialOracle 子表外键需不需要索引

一般情况下, Oracle 子表的外键需要添加索引, 如果外键不添加索引, 一下3种情况会导致 修改父表会锁住子表 1、更新父表主键,

一般情况下, Oracle 子表的外键需要添加索引,

如果外键不添加索引, 一下3种情况会导致 修改父表会锁住子表

1、更新父表主键,子表会被锁住

2、删除父表一行, 整个子表会被锁住

3、合并到父表,子表会被锁住。(9i,,10G是这样,11G不会)。

如果满足以下三种情况,则不需要在外键建立索引

1、没有从父表删除数据

2、没有更新父表主键

3、没有父表关联到子表

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