填空题 A DBMS users can be ____or ____programs.
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填空题 In the history of database design, three models have been in use: the ____model, the ____model, the____model.
填空题 Each column in a relation is called an____.
填空题 Each row in a relation is called a ____.
填空题 A DBMS has three levels: ____,____, and ____.
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