设关系R =(A,B,C),与SQL语句select distinct B from R where A>3 and C = 8等价的关系代数表达式是

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问题 设关系R =(A,B,C),与SQL语句select distinct B from R where A>3 and C = 8等价的关系代数表达式是

选项 A、σA>3 ù C = 8(πB(R))
B、πB(σA>3 ù C = 8(R))
C、πA,B(σA>3 ù C = 8(R))
D、σA>3 ù C = 8(πA,C(R))

答案B

解析
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