在SQL Server中使用count()

本文关键字：count SQL Server | 更新日期: 2023-09-27 18:18:23

下面是我用来从列nos获取计数的代码。

//get max count of orders on server .2
    public int getmaxcountfornos(string caseno,TextBox TextBox3)
    {
        int count2 = 0;
        try
        {
            String dd_webCofig = ConfigurationManager.ConnectionStrings["counton140"].ConnectionString;
            OdbcConnection ddlistconn = new OdbcConnection(dd_webCofig);
            ddlistconn.Open();
            string cnt_2 = "select count(nos) from training_jud.orders where fil_no=@b and jdate=@c";
            OdbcCommand ddlistCmd_2 = new OdbcCommand(cnt_2, ddlistconn);
            ddlistCmd_2.Parameters.AddWithValue("b", caseno);
            ddlistCmd_2.Parameters.AddWithValue("c", Convert.ToDateTime(TextBox3.Text).ToString("yyyy-MM-dd"));
            count2 = (int)ddlistCmd_2.ExecuteScalar();
        }
        catch (Exception ee)
        {
            HttpContext.Current.Response.Write(ee.Message);
        }
        return count2;
    }

这里我得到的异常是

指定的类型转换无效。

有谁能帮我解决这个问题吗?

在SQL Server中使用count()

试试这个:

//get max count of orders on server .2
public int getmaxcountfornos(string caseno,TextBox TextBox3)
{
    int count2 = 0;
    try
    {
        String dd_webCofig = ConfigurationManager.ConnectionStrings["counton140"].ConnectionString;
        OdbcConnection ddlistconn = new OdbcConnection(dd_webCofig);
        ddlistconn.Open();
        string cnt_2 = "select count(nos) from training_jud.orders where fil_no=@b and jdate=@c";
        OdbcCommand ddlistCmd_2 = new OdbcCommand(cnt_2, ddlistconn);
        ddlistCmd_2.Parameters.AddWithValue("**@b**", caseno);
        ddlistCmd_2.Parameters.AddWithValue("**@c**", Convert.ToDateTime(TextBox3.Text).ToString("yyyy-MM-dd"));
        count2 = **Convert.ToInt32**(ddlistCmd_2.ExecuteScalar());
    }
    catch (Exception ee)
    {
        HttpContext.Current.Response.Write(ee.Message);
    }
    return count2;
}

count2 = int.Parse(ddlistCmd_2.ExecuteScalar().ToString());

用上面的代替

count2 = (int)ddlistCmd_2.ExecuteScalar();

问题解决了

到目前为止，你的代码运行良好，但是，请尝试下面的代码部分，谢谢

string cnt_2 = "select count(nos) as OrderCount from training_jud.orders where fil_no=@b and jdate=@c";
OdbcCommand ddlistCmd_2 = new OdbcCommand(cnt_2, ddlistconn);
ddlistCmd_2.Parameters.AddWithValue("@b", caseno);
ddlistCmd_2.Parameters.AddWithValue("@c", Convert.ToDateTime(TextBox3.Text).ToString("yyyy-MM-dd"));
count2 = Convert.ToInt32(ddlistCmd_2.ExecuteScalar());
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