Question

So, what I’m trying to do here is check the user table in my users mySQL database for duplicate entries in the username row, before inserting a new username. Here’s an example of my code. Currently, the results ResultSet does not do anything and I’m not exactly sure how to implement it into the IF statement that follows. And yes, I have the catches for the try, just not in this example. Sorry if this is a rather simple question, I just started programming with Java last week. Also, it’s my first question on here and I definitely appreciate the help.

 try{


      String sequel = ("SELECT username FROM `users`.`user`");
      PreparedStatement userNameInfo = conn.prepareStatement(sequel);
      userNameInfo.executeQuery(sequel);
      ResultSet results = userNameInfo.getResultSet();

      if (sequel.equals("")) {
          conn.setAutoCommit(false);
          String sql = "INSERT INTO `users`.`user`(`username`,`password`,`email`) VALUES('" + newusername +"', '" + newpassword + "', '" + newemail +"')";
          PreparedStatement prest = conn.prepareStatement(sql);
          prest.executeUpdate(sql);
          conn.commit();
          conn.close();
          System.out.println("Added Successfully!");
      }
      else {
          System.out.println("Add failed!");
      }
  }

Answer 1

So I think what you trying to do – and should do I think, is select if the username is in the table then add or not. So the sql needs to be like:

select username from users where username = ?

then set the param in the query. See docs here:
http://docs.oracle.com/javase/6/docs/api/java/sql/PreparedStatement.html

You then need to check what is in the resultset after the query, and see if anything is in there. The API docs for this will be in about the same place as the PreparedStatement docs.

Adding a constraint in the db will also give you a belt and braces.

Hope this helps