插入数据
import java.sql.*;

/**
 * @version 2012-02-22
 * @author
 */
public class InsertDemo {
    public static void main(String[] args) throws SQLException {
        Connection conn = null;
        Statement stmt = null;
        String JDriver="com.microsoft.sqlserver.jdbc.SQLServerDriver";//         String connectDB="jdbc:sqlserver://localhost:1433;DatabaseName=JDBCTest";//        String user="sa";
        String pwd="sql";
        try {
            // 动态导入数据库的驱动
            Class.forName(JDriver);
            // 获取数据库链接
            conn = DriverManager.getConnection(connectDB,user,pwd);
            // 创造SQL语句
            String sql = "INSERT INTO JDBCTestTable ( user_name, user_password ) VALUES ( 'balabala', '123456' )";
            // 执行SQL语句
            stmt = conn.createStatement();
            stmt.executeUpdate(sql);
            System.out.println("插入数据成功");
        } catch (Exception e) {
            e.printStackTrace();
            stmt.close();
            conn.close();
        }
    }
}

修改数据
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class UpdateDemo {

    public static void main(String[] args) throws SQLException {
        Connection conn = null;
        Statement stmt = null;
        try {
            // 动态导入数据库的驱动
            Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
            // 获取数据库链接
            conn = DriverManager.getConnection(
                    "jdbc:sqlserver://localhost:1433;DatabaseName=JDBCTest",
                    "sa", "sql");
            // 创造SQL语句
            String sql = "UPDATE JDBCTestTable SET user_password = '456' WHERE user_name = 'Eric'";
            // 执行SQL语句
            stmt = conn.createStatement();
            stmt.executeUpdate(sql);
            System.out.println("更新数据成功");
        } catch (Exception e) {
            e.printStackTrace();
            stmt.close();
            conn.close();
        }
    }
}

删除数据
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;

public class DeleteDemo {

    public static void main(String[] args){
        String JDriver="com.microsoft.sqlserver.jdbc.SQLServerDriver";
        String url="jdbc:sqlserver://127.0.0.1:1433;DatabaseName=JDBCTest";
        String user="sa";
        String password="sql";
        try{
            Class.forName(JDriver);// 动态导入数据库的驱动
            Connection conn=DriverManager.getConnection(url, user, password);// 获取数据库链接
            String query="DELETE FROM JDBCTestTable WHERE user_name='Eric'";// 创造SQL语句
            Statement stmt=conn.createStatement();// 执行SQL语句
            stmt.executeUpdate(query);
            System.out.println("删除数据成功");
            stmt.close();
            conn.close();
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}

查询数据
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class QueryDemo {

    public static void main(String[] args){
        String JDriver="com.microsoft.sqlserver.jdbc.SQLServerDriver";
        String url="jdbc:sqlserver://127.0.0.1:1433;DatabaseName=JDBCTest";
        String user="sa";
        String password="sql";
        try{
            Class.forName(JDriver);// 动态导入数据库的驱动
            Connection conn=DriverManager.getConnection(url, user, password);// 获取数据库链接
            String query="SELECT * FROM JDBCTestTable";// 创造SQL语句
            Statement stmt=conn.createStatement();// 执行SQL语句
            ResultSet rs=stmt.executeQuery(query);
            while(rs.next()){
                System.out.println(rs.getString("user_name")+":"+rs.getString(2));
                //密码字段的编号从1开始，密码排第二位
            }
            System.out.println("查询数据成功");
            rs.close();
            stmt.close();
            conn.close();
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}