本文介绍了从数据库返回空值的处理方法,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从数据库中选择一个数据,第二次当我从where子句dt1中选择数据时,我得到返回null值没有得到任何错误但是它返回我的空值



我尝试过:



Hello Guys am select a data from database and second time when i select data from with where clause dt1 so i get return null values am not getting any error but it's return me null values

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 dsa2 = new DataSet();
            DataTable dt2 = new DataTable();
            dsa2.Tables.Add(dt2);
            OleDbDataAdapter da2 = new OleDbDataAdapter();
            da2 = new OleDbDataAdapter(string.Format("SELECT column2 FROM Total  Where [Date] between #{0}# AND #{1}#  Group By column2", dateTimePicker1.Text, dateTimePicker2.Text), con_string);
            da2.Fill(dt2);
            con_string.Close();
            //--------------------------------------------------------------------------------
            con_string.ConnectionString = @"Provider = Microsoft.ACE.OLEDB.12.0;Data Source =|DataDirectory|\Restaurant.accdb;Persist Security Info=False";
            con_string.Open();
            DataSet dsa = new DataSet();
            DataTable dt1 = new DataTable();
            dsa.Tables.Add(dt1);
            OleDbDataAdapter da = new OleDbDataAdapter();
            da = new OleDbDataAdapter(string.Format(string.Format("SELECT column2,Sum(MediumVal) As [Dine In], Sum(LargeVal) As [Deliery], Sum(RoyalVal) As [Take Away] From ( SELECT column2 As [column2], Switch(column3 like 'DineIn%', 1,True,0) As [MediumVal], Switch(column3 like 'Delivery%',1,True,0) As [LargeVal], Switch(column3 like 'TakeAway%', 1,True,0) As [RoyalVal] FROM Total  Where [Date] between #{{0}}# AND #{{1}}# AND [column2] IN('{0}') ) Group By column2", dt2.Columns["column2"]), dateTimePicker1.Text, dateTimePicker2.Text), con_string);
            da.Fill(dt1);
            dataGridView1.DataSource = dt1;
            con_string.Close();
            dataGridView1.Columns[0].Width = 286;
            dataGridView1.Columns[1].Width = 180;
            dataGridView1.Columns[2].Width = 180;
            dataGridView1.Columns[3].Width = 180;

推荐答案


FROM Total  Where [Date] between #{{0}}# AND #{{1}}# AND [column2]





应该是





It should be

FROM Total  Where [Date] between #{0}# AND #{1}# AND [column2]


这篇关于从数据库返回空值的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!

07-22 18:54
查看更多