从数据库中获取空值

本文介绍了从数据库中获取空值的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 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.