Read data from mysql - Java JDBC

Java examples for JDBC:MySQL

  1. HOME
  2. Java
  3. JDBC
  4. MySQL

Description

Read data from mysql

Demo Code

import java.io.BufferedReader;
import java.io.FileReader;
import java.sql.*;
import java.util.Date;
import java.util.Random;
import java.util.StringTokenizer;

public class RandomQuery2OnRDB {
    public static void main(String[] args) {
        Connection con = null;//from  w ww.  ja v  a  2 s  .co  m

        try {
            Random rn = new Random();
            try {
                Class.forName("com.mysql.jdbc.Driver");
            } catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            long lStartTime = new Date().getTime();
            System.out.println("start");
            con = DriverManager
                    .getConnection("jdbc:mysql://localhost:3306/?",
                            "asdf", "password");
            try {
                Statement st = con.createStatement();

                String sQuery = "";
                String sQuery_No = "SELECT COUNT(column_name) FROM STATION;";
                ResultSet rs = st.executeQuery(sQuery_No);
                int iCount = 0;
                while (rs.next()) {
                    iCount = rs.getInt(0);
                    System.out.println(iCount + "\n");
                }
                System.out.println("start");

                int iPointOnePercent = (int) ((int) iCount * 0.001);
                int iOnePercent = (int) ((int) iCount * 0.01);
                int iRowNo = 0;
                // Generating 25000 random queries for 0.1 to 1 % of the data
                for (int i = 0; i <= 25000; i++) {

                    int randomInt = rn.nextInt(1);
                    iRowNo = (int) randomInt * iCount;
                    if (iRowNo >= iPointOnePercent && iRowNo <= iOnePercent) {
                        sQuery = "SELECT top " + iRowNo + "FROM weather ";
                        rs = st.executeQuery(sQuery);
                    } else {
                        i--;
                    }
                }
                // calculate time difference for update file time
                long lEndTime = new Date().getTime();
                long difference = lEndTime - lStartTime;
                System.out.println("Elapsed milliseconds: " + difference);
                System.out
                        .println("Elapsed seconds: " + difference * 0.001);

            } catch (SQLException s) {
                s.printStackTrace();
                System.out.println("Table all ready exists!");
            }
            con.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Related Tutorials