在D1输入=if(or(C1="",countif(A:A,C1)=0),"",vlookup(C1,A:B,2,0))即可
D1输入=VLOOKUP(C1,A:B,2,)回车并向下填充
D1中公式:=VLOOKUP(C1,A:B,2,)下拉