C2公式下拉：
=IF(A2="","出货","进货")
或者：
=IF(B2="","进货","出货")
以下公式加入当A列与B列同时为空白时，公式也返回空白：
=IF(A2&B2="","",IF(A2="","出货","进货"))
=if(isblank(a1),"出货","进货")
