ExecuteScalar

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim orden As New OleDbCommand

Dim coneccion As New OleDbConnection(“Provider=Microsoft.Jet.OLEDB.4.0; Data Source=Database2.mbd”)

Dim q As String = “SELECT existencias FROM producto WHERE codigo = ” & TextBox1.Text

Dim stock As Integer

orden = New OleDbCommand(q, coneccion)

orden.Connection.Open()

stock = orden.ExecuteScalar()

orden.Connection.Close()

If stock – Val(TextBox2.Text) < 0 Then

MessageBox.Show(“Stock insuficiente”)

Else

Dim stock2 As Integer = stock – Val(TextBox2.Text)

q = “UODATE producto SET stock = ” + stock2 + ” WHERE codigo = @codigo”

orden.Parameters.Add(New OleDbParameter(“@codigo”, OleDbType.Integer))

orden.Parameters(“@codigo”).Value = TextBox2.Text

orden = New OleDbCommand(q, coneccion)

orden.Connection.Open()

orden.ExecuteNonQuery()

orden.Connection.Close()

End If

End Sub