从数据库中获取空值 [英] Getting null value from database

问题描述

Hello Guys，我正面临一个问题，即我从DB获取值null我在我的数据库中有值，但在我选择时我的表单中我得到null请帮助我怎么做



我尝试了什么：

Hello Guys, I am facing an issue that is I get value null from DB I have values in my DB but in my form when I select so I get null please help me how can I do it

What I have tried:

con_string.ConnectionString = @"Provider = Microsoft.ACE.OLEDB.12.0;Data Source =|DataDirectory|\Restaurant.accdb;Persist Security Info=False";
            con_string.Open();
            DataSet dsa22 = new DataSet();
            DataTable dt22 = new DataTable();
            dsa22.Tables.Add(dt22);
            OleDbDataAdapter da22 = new OleDbDataAdapter();
            string query = "SELECT count(column3) As [QTY]  from [Total] Where [column3] like 'DineIn*'  AND  [Column1] <>0   AND  Cancel  IS NULL And [Date] Between #" + System.DateTime.Now.ToShortDateString() + "# AND #" + System.DateTime.Now.AddDays(1).ToShortDateString() + "# Group By [column3] ";
            da22 = new OleDbDataAdapter(query,con_string);
                      da22.Fill(dt22);
            con_string.Close();
            int sum22 = 0;
            for (int i = 0; i < dsa22.Tables[0].Rows.Count; ++i)
            {
                sum22 += Convert.ToInt32(dsa22.Tables[0].Rows[0][0].ToString());
            }
           Dinein_Orders.Text = sum22.ToString();

推荐答案

就在我的头顶;这样的事情可能会对你有所帮助。

Just off the top of my head; something like this might serve you better.

con_string.ConnectionString = @"Provider = Microsoft.ACE.OLEDB.12.0;Data Source =|DataDirectory|\Restaurant.accdb;Persist Security Info=False";

con_string.Open();

System.Data.IDbCommand cmd = con_string.CreateCommand() ;

cmd.CommandText = "SELECT count(column3) As [QTY]  from [Total] Where [column3] like 'DineIn*'  AND  [Column1] <>0   AND  Cancel  IS NULL And [Date] Between ? AND ? Group By [column3] ";

System.Data.IDbDataParameter prm = cmd.CreateParameter() ;
prm.ParameterName = "?" ;
prm.Value = System.DateTime.Now;
cmd.Parameters.Add ( prm ) ;

prm = cmd.CreateParameter() ;
prm.ParameterName = "?" ;
prm.Value = System.DateTime.Now.AddDays(1) ;
cmd.Parameters.Add ( prm ) ;

Dinein_Orders.Text = cmd.ExecuteScalar().ToString();

con_string.Close();

我希望你'不要将日期存储为字符串。

I do hope you're not storing dates as strings.

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