填空题 Each row in a relation is called a ____.
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填空题 A DBMS has three levels: ____,____, and ____.
填空题 The ____level of a DBMS defines the logic view of the data as well as the data model and schema diagrams.
填空题 The ____is language standardized by ANSI and ISO for use on relation database.
填空题 A ____is a collection of data that is logically, but not necessarily physically, coherent.