could not convert variant of type(null)into type(string) 的错误!
我想把我查询的数据添加到Excel中,但是我一旦运行到Sl:= adoquery3.FieldValues['am']; 这一步,就显示could not convert variant of type(null)into type(string) 的错误!是不是我赋值不能这样,还请大家帮我解决,谢谢!!
部分程序如下:
adoquery3.Close;
adoquery3.SQL.Clear;
adoquery3.SQL.Text := 'select sum(weight)as weight ,sum(am)as am from SMIS_kc where (Mdate in (SELECT MAX(mdate) FROM smis_bal WHERE mdate <= '''+datetostr(dm1.Date)+''' AND name = '''+sname+''' AND color ='''+combobox4.Text+''' )) and color= '''+combobox4.Text+''' and name='''+sname+'''';
adoquery3.Open;
sl:= adoquery3.FieldValues['am'];
zl:= adoquery3.FieldValues['weight'];
excelworksheet1.Cells.item[col,2] := sl;
excelworksheet1.Cells.item[col,3] := zl;