MS Access中带有日期类型参数的SQL语句

Question

I have a SQL statement for querying in MS Access. I want to get the result of the transaction between dates.

This is my code:

 DateTime pFromNew = Convert.ToDateTime(this.dateTimePicker1.Value.ToString("yyyy-MM-dd"));
 DateTime pToNew = Convert.ToDateTime(this.dateTimePicker2.Value.ToString("yyyy-MM-dd"));

 string pFrom = "#" + pFromNew.ToString() + "#";
 string pTo = "#" + pToNew.ToString() + "#";

 chrTrans.Series["Class"].Points.Clear();

 oconn.Open();

 OleDbCommand cmd = oconn.CreateCommand();
 cmd.CommandType = CommandType.Text;

 cmd.CommandText = "Select ClassType,Nametree,TransWeight,Valuedate  from tblTrans where Nametree = '" + this.cboNametree.Text.Trim() + "' and valuedate between '" + pFrom + "' and '" + pTo + "'";
 //+ "' and valuedate between '"+ this.dateTimePicker1.Text +"' and '"+ this.dateTimePicker2.Text +"'";

 cmd.ExecuteNonQuery();

What is wrong with this statement?

I always get this error:

DATA Type mismatch in criteria expression.

Answer 1

Remove the single quotes you have in your string... I will show you...

This line:

cmd.CommandText = "Select ClassType,Nametree,TransWeight,Valuedate  from tblTrans where Nametree = '" + this.cboNametree.Text.Trim() + "' and valuedate between '" + pFrom + "' and '" + pTo + "'";

Should be:

cmd.CommandText = "Select ClassType,Nametree,TransWeight,Valuedate  from tblTrans where Nametree = '" + this.cboNametree.Text.Trim() + "' and valuedate between " + pFrom + " and " + pTo;

The reason is that you already concatenated a # symbol around your date strings--and the single quote thus is not needed.

Answer 2

You are making this too complicated, converting back and forth three times.

It can be reduced to:

string pFrom = "#" + this.dateTimePicker1.Value.ToString("yyyy'/'MM'/'dd") + "#";
string pTo = "#" + this.dateTimePicker2.Value.ToString("yyyy'/'MM'/'dd") + "#";

// snip

cmd.CommandText = "Select ClassType,Nametree,TransWeight,Valuedate from tblTrans where Nametree = '" + this.cboNametree.Text.Trim() + "' and valuedate between " + pFrom + " and " + pTo + "";