Java链接数据库增删改查

链接数据库增删改查"/>

Java链接数据库增删改查

Java链接数据库需要加个jar包。

**注意：**jar报的版本需要跟数据库的版本一致，否则可能会出现异常，不能正常访问数据库。

Java链接数据库的基本操作：增删改查。

把一些重复的内容定义成常量，方便直接调用。

private static final String DRIVER = "com.mysql.cj.jdbc.Driver";
//jar包的位置private static final String URL = "jdbc:mysql://localhost:3306/student_table?characterEncoding=UTF-8&serverTimezone=Asia/Shanghai";//student_table是数据库的名字private static final String USER = "root";//数据库的账号private static final String PASSWORD ="456789";//数据库的密码

查询数据库表里的内容：

/*** 查询功能*/public static void query(){//先定义成空值，防止表是空表。Connection conn = null;Statement statement = null;ResultSet rs = null;try {//注册驱动Class.forName(DRIVER);//登录数据库获取链接对象conn = DriverManager.getConnection(URL, USER, PASSWORD);//定义SQL//这个是库里面的表的结构，和来自哪个表名String sql = "select s_id,s_name,s_birth,s_sex from student";//执行SQL 需要Statement对象statement = conn.createStatement();//执行SQL获取结果集rs = statement.executeQuery(sql);//遍历结果集（查询的过程中，可能会出现查询结果为空）while(rs.next()){//判断是否有下一个元素，每次循环都代表一行数据//获取元素一行中的列String s_id = rs.getString("s_id");String s_name = rs.getString("s_name");String s_birth = rs.getString("s_birth");String s_sex = rs.getString("s_sex");System.out.println(s_id+"--"+s_name+"--"+s_birth+"--"+s_sex);}} catch (ClassNotFoundException e) {e.printStackTrace();} catch (SQLException e) {e.printStackTrace();}//前面设置空值就是用在这里，如果是空值，就不用关闭了finally{try {if(rs != null){rs.close();}if(statement != null){statement.close();}if(conn != null){conn.close();}}catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}

修改数据库的内容：

/*** 修改*/public static void update(){Connection conn = null;Statement statement = null;try {//注册驱动Class.forName(DRIVER);//登录数据库连接对象conn = DriverManager.getConnection(URL, USER, PASSWORD);String sql = "update student set s_name='小豪' where s_id=9";statement = conn.createStatement();int result = statement.executeUpdate(sql);System.out.println(result);} catch (ClassNotFoundException e) {e.printStackTrace();} catch (SQLException e) {e.printStackTrace();}finally{try {if(statement != null){statement.close();}if(conn != null){conn.close();}}catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}

添加数据库的内容：

/*** 添加数据*/public static void insert(){Connection conn = null;Statement statement = null;try {//注册驱动Class.forName(DRIVER);//登录数据库连接对象conn = DriverManager.getConnection(URL, USER, PASSWORD);String sql = "insert into student values(9,'张小豪','2222-02-22','女')";statement = conn.createStatement();int result = statement.executeUpdate(sql);System.out.println(result);} catch (ClassNotFoundException e) {e.printStackTrace();} catch (SQLException e) {e.printStackTrace();}finally{try {if(statement != null){statement.close();}if(conn != null){conn.close();}}catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}

删除数据库内容：

/*** 删除数据*/public static void delete(){Connection conn = null;Statement statement = null;try {//注册驱动Class.forName(DRIVER);//登录数据库连接对象conn = DriverManager.getConnection(URL, USER, PASSWORD);String sql = "delete from student where s_id=9";statement = conn.createStatement();int result = statement.executeUpdate(sql);System.out.println(result);} catch (ClassNotFoundException e) {e.printStackTrace();} catch (SQLException e) {e.printStackTrace();}finally{try {if(statement != null){statement.close();}if(conn != null){conn.close();}}catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}