19.7. Retrieving Database Records

You can retrieve records from the database via a SELECT command. In order to execute a SELECT command you need to do the following:

1. Create and open a database connection

2. Create a EDBCommand object representing the Select statement to execute

3. Execute the command with the ExecuteReader() method of the EDBCommand object returning a EDBDataReader

4. Loop through the EDBDataReader displaying the results or binding the EDBDataReader to some control.

A EDBDataReader represents a forward-only and read-only stream of database records where we can only get one record at a time. Each time we want to read the next record we must call the read() method of the EDBDataReader object.

The following example demonstrates the use of a EDBDataReader in conjunction with a SQL Select statement

   
<% @ Page Language="C#" %>
<% @Import Namespace="EnterpriseDB.EDBClient" %>
<% @Import Namespace="System.Data" %>

<script language="C#" runat="server">

private void Page_Load(object sender, System.EventArgs e)
{
	string strConnectionString = ConfigurationSettings.AppSettings["DB_CONN_STRING"];
	EDBConnection conn = new EDBConnection(strConnectionString);	
			
	try {
		conn.Open();
		EDBCommand cmdSelect = new EDBCommand("SELECT * FROM dept",conn);
		cmdSelect.CommandType = CommandType.Text;					
		EDBDataReader drDept = cmdSelect.ExecuteReader();
				
		while(drDept.Read()) {
			Response.Write("Department Number: " + drDept["deptno"]);
			Response.Write("\tDepartment Name: " + drDept["dname"]);
			Response.Write("\tDepartment Location: " + drDept["loc"]);
			Response.Write("<br>");
		}
				
	}
	
	catch(Exception exp) { 
		Response.Write(exp.ToString());
	}
	finally {
		conn.Close();
	}
}		
</script>

   

Save the file as "selectEmployees.aspx" and save it in your default web root, and access it by typing http://localhost/selectEmployees.aspx in your browser window. Given that your connection information is correct and you have installed the sample EDB database you should see the following upon the successful execution of this query.