compare sql resultset with a String

[cotarelo]

Hi,

I want to compare the resultset obtained by a sql query with a string. So what I want is when the word queried is inside the database, do a set of actions...

public void run(){
		try{
			input = new BufferedReader(new InputStreamReader(s.getInputStream()));
                        String url = "jdbc:mysql://localhost/mydatabase";
                        Connection con = DriverManager.getConnection(url, "user", "password");
                           
                        
			while (true){
				String str = input.readLine();
				System.out.println("Receiving: " + str);
                                System.out.println("Checking if the word received it is on the database");
                                Statement select2 = con.createStatement();
                                ResultSet actualsituation = select2.executeQuery("SELECT ifx FROM table WHERE ifx='"+str+"';");


                                if (actualsituation.equals(str)){
                                    System.out.println("Lets retreive the whole file");
...
...

But in the line

                                if (actualsituation.equals(str)){

I can't compare those 2 variables... how to compare a string with the values received from the database? (resultset object)

[PhHein]

You have to open the resultSet or check whether it is not empty:

 ResultSet actualsituation = select2.executeQuery("SELECT ifx FROM table WHERE ifx='"+str+"';");
if (actualsituation.next()){ // rs.next() is false if nothing is found
    System.out.println("Lets retreive the whole file");

And you should use preparedStatements to avoid SQL injection, read this tutorial: http://java.sun.com/docs/books/tutorial/jdbc/index.html

[cotarelo]

Thanks!

Now I am thinking that I am doing it too complicated... is there any easy way to query a mysql database and receive true if the string is inside the database and false if it is not?

Thanks again!

[PhHein]

You're welcome. No that is the easy way. ;-)

[cotarelo]

Right! is the easy way!

so exactly, if the query is true, it will go on the if bucle, if not it will jump it :)

I did not understand it at the beggining.

PS:Now it works but I have another problem, so I will open a new thread :)

[PhHein]

If it's about databases use the JDBC forum.

[cotarelo]

Well I am not sure... I think it is related to sockets or databases, I dont know...

The thing is that the string str is retreived from a socket, and, a few seconds after retreiving the values with jdbc and storing them, in the console I receive a infinite loop that looks like this:

Receiving: null
Checking if the word received it is on the database
Receiving: null
Checking if the word received it is on the database
Receiving: null
Checking if the word received it is on the database
Receiving: null
Checking if the word received it is on the database
Receiving: null
Checking if the word received it is on the database

And so on