给定关系R(A,B,C,D,E)与S(B,C,F,G),那么与表达式π2,4,6,7(σ2<7(RS))等价的SQL语句如下: SELECT (41)________________ FROM R,S WHERE (42)______________

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问题 给定关系R(A,B,C,D,E)与S(B,C,F,G),那么与表达式π2,4,6,72<7(RS))等价的SQL语句如下:
  SELECT (41)________________  FROM R,S WHERE (42)________________;

选项 A、R.B,D,F,G
B、R.B.E,S.C,F,G
C、R.B,R.D,S.C,F
D、R.B,R.C,S.C,F

答案A

解析
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