Home

ODP.NET - OracleCommand Object

Author: Packt Publishing Published on: 5th Apr 2008 | Last Updated on: 9th Apr 2008

ODP.NET - More About the OracleCommand Object

Till now, we have seen OracleCommand working with OracleDataReader. OracleCommand is not simply meant for OracleDataReader. It has got a lot of functionality for itself. Let us see few of the most commonly used features of OracleCommand in this section. We will further go into depth in subsequent sections and chapters.

Ads

Retrieving a Single Value from the Database

As we already covered working with single or multiple rows, we need to work on retrieving a single value from database very effectively. We have already retrieved row values in our previous examples, but those examples are more suitable when you are trying to deal with entire rows.

OracleCommand is equipped with a method called ExecuteScalar, which is mainly used to retrieve single values from the database very efficiently thus improving the performance. The following example focuses on this:

Sample Code

Imports Oracle.DataAccess.Client
Public Class Form9
Private Sub btnEmployeeCount_Click(ByVal sender As
System.Object, ByVal e As System.EventArgs) Handles
btnEmployeeCount.Click
'create connection to db
Dim cn As New OracleConnection("Data Source=xe; _
User Id=scott;Password=tiger")
Try
'create the command object
Dim cmd As New OracleCommand("SELECT COUNT(*) _
FROM emp", cn)
'open the connection from command
cmd.Connection.Open()
'execute the command and get the single value
'result
Dim result As String = cmd.ExecuteScalar
'clear the resources
cmd.Connection.Close()
cmd.Dispose()
'display the output
MessageBox.Show("No. of Employees: " & result)
Catch ex As Exception
'display if any error occurs
MessageBox.Show("Error: " & ex.Message)
'close the connection if it is still open
If cn.State = ConnectionState.Open Then
cn.Close()
End If
End Try
End Sub
End Class

Ads

The highlighted line in the above code simply executes the SELECT command, which retrieves the number of rows from the emp table and assigns this value to the result variable.

This tutorial is part of a ODP.NET tutorial series. Read it from the beginning and learn yourself.

ODP.NET