试题详情

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( 2<7(R S))等价的SQL SELECT(请作答此空FROM R,S WHERE( );

AR.B=S.B OR R.C=S.C OR R.B<S.G

BR.B=S.B OR R.C=S.C OR R.B<S.C

CR.B=S.B AND R.C=S.C AND R.B<S.G

DR.B=S.B AND R.C=S.C AND R.B<S.C