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单选

在局部E-R图合并为总体E-R图的过程中,(59)是错误的。

  • A.不同局部E-R图中出现的相同实体,在总体E-R图中只能出现一次
  • B.在总体E-R图中可以添加属于不同局部E-R图实体间的联系
  • C.在总体E-R图中可以删除在原局部E-R图中存在的联系
  • D.在总体E-R图中不能删除任何不同实体间的联系
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