using System;

public class Program

{

    public static void Main()

    {

        String s = "select * from tab where user="+"';delete from tab;--"+" and pers_no is not null";

      //Console.WriteLine("The initial string: '{0}'", s);

      s = s.Replace('\'','\0').Replace(';','\0').Replace('-','\0');

      Console.WriteLine("The final string: {0}", s);    

    }

}