JDBC基本语法

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;

/**
 * JDBC快速入门
 */
public class JdbcDemo1 {
    public static void main(String[] args) throws Exception {

        //1. 导入驱动jar包
        //2.注册驱动
        Class.forName("com.mysql.jdbc.Driver");
        //3.获取数据库连接对象
        /*
        Connection的格式为jdbc:数据库类型://数据库ip地址：数据库端口号/数据库名称,登录名称,登录密码
        Connection conn = 
            DriverManager.getConnection("jdbc:mysql://localhost:3306/db3", "root", "root");
        如果数据库是本地数据库，可以把localhost:3306直接删掉
         */
        Connection conn = DriverManager.getConnection("jdbc:mysql:///db3", "root", "root");
        //4.定义sql语句，修改db3数据库中自定义account表里的balance一列的数据为2000
        String sql = "update account set balance = 2000";
        //5.获取执行sql的对象 Statement
        Statement stmt = conn.createStatement();
        //6.执行sql
        int count = stmt.executeUpdate(sql);
        //7.处理结果
        System.out.println(count);
        //8.释放资源
        stmt.close();
        conn.close();
    }
}

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * account表 添加一条记录 insert 语句
 */
public class JDBCDemo2 {
    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try {
            //1. 注册驱动
            Class.forName("com.mysql.jdbc.Driver");
            //2. 定义sql
            String sql = "insert into account values(null,'王五',3000)";
            //3.获取Connection对象
            conn = DriverManager.getConnection("jdbc:mysql:///db3", "root", "root");
            //4.获取执行sql的对象 Statement
            stmt = conn.createStatement();
            //5.执行sql，其中count的意义是：代码执行后受影响的行数
            int count = stmt.executeUpdate(sql);
            //6.处理结果
            System.out.println(count);
            if(count > 0){
                System.out.println("添加成功！");
            }else{
                System.out.println("添加失败！");
            }

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            //stmt.close();
            //7. 释放资源
            //避免空指针异常
            if(stmt != null){
                try {
                    stmt.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }

            if(conn != null){
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * account表 修改记录
 */
public class JDBCDemo3 {
    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try {
            //1. 注册驱动
            Class.forName("com.mysql.jdbc.Driver");
            //2.获取连接对象
            conn = DriverManager.getConnection("jdbc:mysql:///db3", "root", "root");
            //3.定义sql，将account表的的id为3的balance字段数据更改为1500
            String sql  = "update account set balance = 1500 where id = 3";
            //4.获取执行sql对象
            stmt = conn.createStatement();
            //5.执行sql
            int count = stmt.executeUpdate(sql);
            //6.处理结果
            System.out.println(count);
            if(count > 0){
                System.out.println("修改成功！");
            }else{
                System.out.println("修改失败");
            }

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            //7.释放资源
            if(stmt != null){
                try {
                    stmt.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }

            if(conn != null){
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

import cn.itcast.util.JDBCUtils;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * account表 删除一条记录
 */
public class JDBCDemo4 {
    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try {
            //1. 注册驱动
            Class.forName("com.mysql.jdbc.Driver");
            //2.获取连接对象
            conn = DriverManager.getConnection("jdbc:mysql:///db3", "root", "root");
            //3.定义sql
            String sql  = "delete from account where id = 3";
            //4.获取执行sql对象
            stmt = conn.createStatement();
            //5.执行sql
            int count = stmt.executeUpdate(sql);
            //6.处理结果
            System.out.println(count);
            if(count > 0){
                System.out.println("删除成功！");
            }else{
                System.out.println("删除失败");
            }

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            //7.释放资源

            if(stmt != null){
                try {
                    stmt.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }

            if(conn != null){
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

import java.sql.*;

/**
 * 执行DDL语句
 */
public class JDBCDemo6 {
    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;
        try {
            //1. 注册驱动
            Class.forName("com.mysql.jdbc.Driver");
            //2.获取连接对象
            conn = DriverManager.getConnection("jdbc:mysql:///db3", "root", "root");
            //3.定义sql
            String sql  = "select * from account";
            //4.获取执行sql对象
            stmt = conn.createStatement();
            //5.执行sql
            rs = stmt.executeQuery(sql);
            //6.处理结果
            //6.1 让游标向下移动一行，刚开始的游标是在表头，得向下一行才能有数据
            rs.next();
            //6.2 获取数据
            int id = rs.getInt(1);
            String name = rs.getString("name");
            double balance = rs.getDouble(3);
            System.out.println(id + "---" + name + "---" + balance);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            //7.释放资源
            if(rs != null){
                try {
                    rs.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }

            if(stmt != null){
                try {
                    stmt.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }

            if(conn != null){
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}