=SUM(if(b2:b100=a1,c2:c100,0))数组公式,按ctrl+shift+回车结束
=IF(COUNTIF(B2:B100,A1),VLOOKUP(A1,B2:C100,2,),)
=SUMIF(B:B,A1,C:C)
sumif(B:B,A1,C1)