How can I print column sections from SQL to Java to CSV?

Question

I have set up a MySQL database, my connection works, and I've somewhat got a handle on how to retrieve data from the database using ResultSet. The issue I'm currently having is that the assignment calls for certain columns from a few different tables to be printed in CSV format along with replacing some values that meet certain conditions; i.e., if the cost of a plane ticket for a particular flight is under a certain price, replace the cost with "LOW!" in that part of the CSV file. Here's what I've got:

public void generate() throws IOException, SQLException{

    FileWriter fw = new FileWriter("datamine.csv");
    PrintWriter out = new PrintWriter(fw);
    Statement st = conn.createStatement();

    out.println("Airline,FlightNumber,Source,Destination,DayOfWeek,Seats,Daysbefore,Price");

    //ResultStatements here

    out.flush();
    out.close();
    fw.close();

}

I know how to query the DB, and I think I can figure out how to union the columns from tables that I need, but that will just print everything in the column. Is there a way to iterate through the columns, evaluate the value for conditionals, and then append it to the output file?

JB Nizet · Accepted Answer · 2013-04-14 21:56:13Z

1

You need a while loop, and an if test.

while (rs.next()) {

    String airline = rs.getString(1);
    ...
    BigDecimal price = rs.getBigDecimal(8);
    if (price.compareTo(limit) < 0) {
        csvFile.print("LOW!");
    }
    else {
        csvFile.print(price);
    }
}

answered Apr 14, 2013 at 21:56

JB Nizet

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