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Sorting Data

This chapter provides an example on how to sort records from a table using JDBC application. This would use asc and desc keywords to sort records in ascending or descending order. Before executing the following example, make sure you have the following in place:

To execute the following example you can replace the username and password with your actual user name and password.
Your MySQL or whatever database you are using, is up and running.

Required Steps

The following steps are required to create a new Database using JDBC application:

Import the packages: Requires that you include the packages containing the JDBC classes needed for database programming. Most often, using import java.sql.* will suffice.
Register the JDBC driver: Requires that you initialize a driver so you can open a communications channel with the database.
Open a connection: Requires using the DriverManager.getConnection() method to create a Connection object, which represents a physical connection with a database server.
Execute a query: Requires using an object of type Statement for building and submitting an SQL statement to sort records from a table. These Queries make use of asc and desc clauses to sort data in ascending and descening orders.
Clean up the environment: Requires explicitly closing all database resources versus relying on the JVM's garbage collection.

Sample Code

Copy and paste the following example in JDBCExample.java, compile and run as follows:

//STEP 1. Import required packages
import java.sql.*;
public class JDBCExample {
// JDBC driver name and database URL
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
static final String DB_URL = "jdbc:mysql://localhost/STUDENTS";
// Database credentials
static final String USER = "username";
static final String PASS = "password";
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
try{
//STEP 2: Register JDBC driver
Class.forName("com.mysql.jdbc.Driver");
//STEP 3: Open a connection
System.out.println("Connecting to a selected database...");
conn = DriverManager.getConnection(DB_URL, USER, PASS);
System.out.println("Connected database successfully...");
//STEP 4: Execute a query
System.out.println("Creating statement...");
stmt = conn.createStatement();
// Extract records in ascending order by first name.
System.out.println("Fetching records in ascending order...");
String sql = "SELECT id, first, last, age FROM Registration" +
" ORDER BY first ASC";
ResultSet rs = stmt.executeQuery(sql);
while(rs.next()){
//Retrieve by column name
int id = rs.getInt("id");
int age = rs.getInt("age");
String first = rs.getString("first");
String last = rs.getString("last");
//Display values
System.out.print("ID: " + id);
System.out.print(", Age: " + age);
System.out.print(", First: " + first);
System.out.println(", Last: " + last);
}
// Extract records in descending order by first name.
System.out.println("Fetching records in descending order...");
sql = "SELECT id, first, last, age FROM Registration" +
" ORDER BY first DESC";
rs = stmt.executeQuery(sql);
while(rs.next()){
//Retrieve by column name
int id = rs.getInt("id");
int age = rs.getInt("age");
String first = rs.getString("first");
String last = rs.getString("last");
//Display values
System.out.print("ID: " + id);
System.out.print(", Age: " + age);
System.out.print(", First: " + first);
System.out.println(", Last: " + last);
}
rs.close();
}catch(SQLException se){
//Handle errors for JDBC
se.printStackTrace();
}catch(Exception e){
//Handle errors for Class.forName
e.printStackTrace();
}finally{
//finally block used to close resources
try{
if(stmt!=null)
conn.close();
}catch(SQLException se){
}// do nothing
try{
if(conn!=null)
conn.close();
}catch(SQLException se){
se.printStackTrace();
}//end finally try
}//end try
System.out.println("Goodbye!");
}//end main
}//end JDBCExample

Now, let us compile the above example as follows:

C:\>javac JDBCExample.java
C:\>

When you run JDBCExample, it produces the following result:

C:\>java JDBCExample
Connecting to a selected database...
Connected database successfully...
Creating statement...
Fetching records in ascending order...
ID: 103, Age: 28, First: Sumit, Last: Mittal
ID: 102, Age: 30, First: Zaid, Last: Khan
ID: 100, Age: 30, First: Zara, Last: Ali
Fetching records in descending order...
ID: 100, Age: 30, First: Zara, Last: Ali
ID: 102, Age: 30, First: Zaid, Last: Khan
ID: 103, Age: 28, First: Sumit, Last: Mittal
Goodbye!
C:\>

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Sorting Data