WHERE 1=1 ${if(len(工单编号) == 0,"","and MONO= '" + 工单编号 + "'")} ${if(len(品号) == 0,"","and B.PRODUCTNO= '" + 品号 + "'")}${if(len(流水号) == 0,"","and LOTNO= '" + 流水号+ "'")}${if(len(生产批状态) == 0,"","and STATUS= '" + 生产批状态 + "'")}${if(len(工序名称) == 0,"","and C.OPNAME= '" + 工序名称 + "'")}${if(len(工序编号) == 0,"","and C.OPNO='" + 工序编号 + "'")}疑问：品号前后的'+'是什么意思？
