单选题 The relation is a set of data organized logically as a (n)()-dimensional table.
A. one
B. two
C. three
D. any
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单选题 Each column in a relation is called ().
A. an attribute
B. a tuple
C. a union
D. an attitude
单选题 The degree of a relation is the number of () in the relation.
A. attributes
B. tuples
C. unions
D. attitudes
单选题 Each row in a relation is called ().
A. an attribute
B. a tuple
C. a union
D. an attitude
单选题 If a relation has five rows, then its () is five.
A. difference
B. cardinality
C. duplicity
D. relativity