问题
单项选择题
What operation on relations R and S produces the relation shown below { tuple | tuple∈R ∨ tuple∈S} ( )
A．union
B．difference
C．intersection
D．division
答案
参考答案：A
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What operation on relations R and S produces the relation shown below { tuple | tuple∈R ∨ tuple∈S} ( )
A．union
B．difference
C．intersection
D．division
参考答案：A