本教學介紹了如何使用JDBC應用程序的對表中的數據進行排序的例子。這將使用asc和desc關鍵字的記錄按升序或降序排序。執行下麵的示例之前，請確保如下：

• 執行下麵的例子中，請使用實際的用戶名和密碼代替username和password。

• MySQL或者其他數據庫，正在使用：啟動和運行。

所需步驟：

使用JDBC應用程序創建一個新的數據庫需要執行以下步驟：

• 導入包：要求包括含有需要進行數據庫編程的JDBC類的包。大多數情況下，使用 import java.sql.* 。

• 注冊JDBC驅動程序：要求初始化驅動程序，使它可以與數據庫打開一個通信通道。

• 打開一個連接：要求使用DriverManager.getConnection()方法創建一個Connection對象，它代表與數據庫服務器的物理連接。

• 執行一個查詢：需要使用類型語句的對象建立並提交一個SQL語句的記錄從表中進行排序。查詢利用ASC和DESC子句來按升序和降序順序排序數據。

• 清理環境：需要明確地關閉所有的數據庫資源相對於依靠JVM的垃圾收集。

示例代碼：

複製過去的下麵的例子中JDBCExample.java，編譯並運行，如下所示：

//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

現在編譯上麵的例子如下：

C:>javac JDBCExample.java
C:>

當運行JDBCExample，它會產生以下結果：

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:>