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]
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