在SQL查询中计算空值 [英] calculate null value in sql query

问题描述

cmd = new OleDbCommand("select sum(Net_Total) FROM Factory_Pay where Factory_Name='" + comboBox1.Text + "'", con);
                    dr = cmd.ExecuteReader();
                    while (dr.Read())
                    {
                        if (dr.HasRows)
                        {
                            double dd = Convert.ToDouble(dr[0].ToString());
                            label1.Text = "Grand Total  :  " + dd.ToString("0,0.00", CultureInfo.CreateSpecificCulture("Hi-In"));
                        }
                        else
                        {
                            MessageBox.Show("No Record found", "Information", MessageBoxButtons.OK, MessageBoxIcon.Information);
                        }
                    }
                    dr.Close();

我正在使用此代码来计算总金额，但是我收到了一些错误消息，因为表中的工厂名称列可用，但Net_Total列包含空值....

错误消息为:输入字符串的格式不正确"；


所以任何人都可以帮助我..

i m using this code to calculate total amount but i got some error msg because factory name column available in table but Net_Total column contain null value....

error msg is : "Input string was not in correct formate ";


so any one help me..

推荐答案

尝试一下:

Try this:

cmd = new OleDbCommand("select sum(Net_Total) FROM Factory_Pay where Factory_Name='" + comboBox1.Text + "'", con);
dr = cmd.ExecuteReader();
while (dr.Read())
{
    if (dr.HasRows)
    {
        //Here from database some values are coming null. You need to check for null values also
        if(dr[0] != DBNull.Value){
            double dd = Convert.ToDouble(dr[0].ToString());
            label1.Text = "Grand Total  :  " + dd.ToString("0,0.00", CultureInfo.CreateSpecificCulture("Hi-In"));
        }
    }
    else
    {
        MessageBox.Show("No Record found", "Information", MessageBoxButtons.OK, MessageBoxIcon.Information);
    }
}
dr.Close();

--Amit

--Amit

从Factory_Pay中选择isull(sum(isnull(Net_Total，0))，0)，其中Factory_Name =''

select isnull(sum(isnull(Net_Total,0)),0) FROM Factory_Pay where Factory_Name=''

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