Cannot use DESCRIBE or EXECUTE on a statement that is not
  prepared

  Explanation:  Either you attempted to use a DESCRIBE or EXECUTE
  statement which named a statement that was not successfully
  prepared, or you passed a non-zero statement-id to PREPARE which
  is not a valid statement.

  User Action:  Prepare the statement before calling DESCRIBE or
  EXECUTE, or set the statement-id to zero before calling PREPARE.