A.r={R1(A1,A2,A3),R2(A3,A4,A5),R3(A5,A6,A7)}B.r={R1(A1,A2,A3,A4,A5),R2(A5,A6,A7)}C.r={R1(A1,A2,A3),R2(A3,A4,A5,A6,A7)}D.r={R1(A2,A3,A6,A7),R2(A1,A4,A5)}E.其他都不对。
A.r={R1(A2,A3,A5),R2(A1,A3,A6),R3(A2,A4,A6)}B.r={R1(A2,A3,A5),R2(A1,A3,A6),R3(A2,A4,A6),R4(A1,A2)}C.r={R1(A2,A3,A5),R2(A1,A2,A3,A4,A6)}D.r={R1(A1,A2,A3,A5),R2(A2,A4,A6)}
A.既具有无损连接性,又保持函数依赖B.不具有无损连接性,但保持函数依赖C.具有无损连接性,但不保持函数依赖D.既不具有无损连接性,又不保持函数依赖