Noob help- SQL syntax

I have a request.form. Users view their information by typing their phone number. Works fine, but I need to know how to create a user friendly error message when the phone field is empty. Here's my code:

<%
  'variables
  dim Conn, Connstring, Sql_Get, TheArray, Recordset
 
  'database connection
  Set Conn = Server.CreateObject("ADODB.Connection")
  Conn.Provider = provider
  Conn.ConnectionString = dbasepath
  Conn.Open

' Sql statement
  Sql_Get="SELECT * FROM tblFestival WHERE Phone='" & Request.Form("Phone") & "'"

Set Recordset = Conn.Execute(Sql_Get)

' get the recordset data in memory using getrows()
  TheArray = RecordSet.Getrows

' Cleanup objects
  Conn.Close
  Set Conn = Nothing
  Set RecordSet = Nothing
   %>

Any help much appreciated. Sorry if this is a noob-q, but I'm kinda stuck.

Thanks,
OMG