若在Rating表上建立如下的参照完整性约束： FOREIGN KEY （rID ) REFERENCES Reviewer （rID ) ON UPDATE CASCADE ON DELETE SET NULL FOREIGN KEY （mID ) REFERENCES Movie （mID ) ON DELETE CASCADE 则当更新Reviewer表中的rID字段和更新Movie表中的mID字段时，系统的反应分别是——A．均不做参照完整性检查，可以随意更新两个表中的连接字段值B．若Rating表中有相关参照记录，则Reviewer表的更新操作被禁止，Movie表的更新操作同时自动更新Rating表中记录的对应参照字段C．若Rating表中有相关参照记录，则Reviewer表的更新操作同时自动更新Rating表中记录的对应参照字段，Movie表的更新操作被禁止D．若Rating表中有相关参照记录，则均两个表的更新操作均被禁止
若在Rating表上建立如下的参照完整性约束： FOREIGN KEY （rID ) REFERENCES Reviewer （rID ) ON UPDATE CASCADE ON DELETE SET NULL FOREIGN KEY （mID ) REFERENCES Movie （mID ) ON DELETE CASCADE 则当更新Reviewer表中的rID字段和更新Movie表中的mID字段时，系统的反应分别是——
A．均不做参照完整性检查，可以随意更新两个表中的连接字段值
B．若Rating表中有相关参照记录，则Reviewer表的更新操作被禁止，Movie表的更新操作同时自动更新Rating表中记录的对应参照字段
C．若Rating表中有相关参照记录，则Reviewer表的更新操作同时自动更新Rating表中记录的对应参照字段，Movie表的更新操作被禁止
D．若Rating表中有相关参照记录，则均两个表的更新操作均被禁止
参考答案和解析
若Rating表中有相关参照记录，则Reviewer表的更新操作同时自动更新Rating表中记录的对应参照字段，Movie表的更新操作被禁止
相关考题：
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