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+### JDBC作业：
+
+1. MySQL中创建一个数据库student_db
+
+2. 库中创建student表
+
+3. 表中数据如下
+
+4. | 编号 | 姓名 | 性别 |
+   | ---- | ---- | ---- |
+   | 1    | 张三 | 男   |
+   | 2    | 李四 | 女   |
+   | 3    | 王五 | 男   |
+
+5. 编写java 4个类，分别实现以下功能
+
+   查询功能，查询student中所有数据
+
+   ```java
+   try {
+               Class.forName("com.mysql.jdbc.Driver");
+               String url = "jdbc:mysql://localhost:3306/text?useSSL=false&useUnicode=true&characterEncoding=utf8";
+               String username = "root";
+               String password = "root";
+               Connection conn = DriverManager.getConnection(url,username,password);
+               String sql = "select * from student";
+               Statement st = conn.createStatement();
+               ResultSet re = st.executeQuery(sql);
+               System.out.println("编号\t\t姓名\t\t性别");
+               while (re.next()) {
+                   int id = re.getInt(1);
+                   String name = re.getString(2);
+                   String sex = re.getString(3);
+                   System.out.println(id+"\t\t"+name+"\t\t"+sex);
+               }
+               re.close();
+               st.close();
+               conn.close();
+           } catch (ClassNotFoundException e) {
+               throw new RuntimeException(e);
+           } catch (SQLException e) {
+               throw new RuntimeException(e);
+           }
+   ```
+
+   添加功能
+
+   ```java
+   try {
+               Class.forName("com.mysql.jdbc.Driver");
+               String url = "jdbc:mysql://localhost:3306/student_db?useSSL=false&useUnicode=true&characterEncoding=utf8";
+               String username = "root";
+               String password = "root";
+               Connection conn = DriverManager.getConnection(url,username,password);
+               String sql = "insert into student values(4,'A','男')";
+               Statement st = conn.createStatement();
+               int i = st.executeUpdate(sql);
+               System.out.println("添加了"+i+"行");
+               st.close();
+               conn.close();
+           } catch (ClassNotFoundException e) {
+               throw new RuntimeException(e);
+           } catch (SQLException e) {
+               throw new RuntimeException(e);
+           }
+   ```
+
+   修改功能
+
+   ```java
+   try {
+               Class.forName("com.mysql.jdbc.Driver");
+               String url = "jdbc:mysql://localhost:3306/student_db?useSSL=false&useUnicode=true&characterEncoding=utf8";
+               String username = "root";
+               String password = "root";
+               Connection conn = DriverManager.getConnection(url,username,password);
+               String sql = "update student set name = 'B' where name = 'A'";
+               Statement st = conn.createStatement();
+               int i = st.executeUpdate(sql);
+               System.out.println("修改了"+i+"行");
+               st.close();
+               conn.close();
+           } catch (ClassNotFoundException e) {
+               throw new RuntimeException(e);
+           } catch (SQLException e) {
+               throw new RuntimeException(e);
+           }
+   ```
+
+   删除功能
+
+   ```java
+   try {
+               Class.forName("com.mysql.jdbc.Driver");
+               String url = "jdbc:mysql://localhost:3306/student_db?useSSL=false&useUnicode=true&characterEncoding=utf8";
+               String username = "root";
+               String password = "root";
+               Connection conn = DriverManager.getConnection(url,username,password);
+               String sql = "delete from student where id = 1";
+               Statement st = conn.createStatement();
+               int i = st.executeUpdate(sql);
+               System.out.println("删除了"+i+"行");
+               st.close();
+               conn.close();
+           } catch (ClassNotFoundException e) {
+               throw new RuntimeException(e);
+           } catch (SQLException e) {
+               throw new RuntimeException(e);
+           }
+
+6. 扩展题【预习题】
+
+   1. 能否实现一个类中，用四个方法来实现上面4个类的功能
+   2. 能否实现将查询的结果，封装成java对象
+   
+   ```java
+   import java.sql.*;
+   
+   public class Jdbc {
+   
+       //注册+连接
+       Connection conn() {
+           try {
+               Class.forName("com.mysql.jdbc.Driver");
+               String url = "jdbc:mysql://localhost:3306/student_db?useSSL=false&useUnicode=true&characterEncoding=utf8";
+               String username = "root";
+               String password = "root";
+               Connection conn = DriverManager.getConnection(url, username, password);
+               Statement st = conn.createStatement();
+               return conn;
+           } catch (ClassNotFoundException e) {
+               throw new RuntimeException(e);
+           } catch (SQLException e) {
+               throw new RuntimeException(e);
+           }
+       }
+   
+       //添加
+       void add(String sql){
+           Connection conn = conn();
+           try {
+               Statement st = conn.createStatement();
+               int i = st.executeUpdate(sql);
+               System.out.println("添加了"+i+"行");
+               st.close();
+               conn.close();
+           } catch (SQLException e) {
+               throw new RuntimeException(e);
+           }
+       }
+   
+       //删除
+       void delete(String sql){
+           Connection conn = conn();
+           try {
+               Statement st = conn.createStatement();
+               int i = st.executeUpdate(sql);
+               System.out.println("删除了"+i+"行");
+               st.close();
+               conn.close();
+           } catch (SQLException e) {
+               throw new RuntimeException(e);
+           }
+       }
+   
+       //修改
+       void update(String sql){
+           Connection conn = conn();
+           try {
+               Statement st = conn.createStatement();
+               int i = st.executeUpdate(sql);
+               System.out.println("修改了"+i+"行");
+               st.close();
+               conn.close();
+           } catch (SQLException e) {
+               throw new RuntimeException(e);
+           }
+       }
+   
+       //查询
+       void select(String sql){
+           Connection conn = conn();
+           try {
+               Statement st = conn.createStatement();
+               ResultSet re = st.executeQuery(sql);
+               System.out.println("编号\t\t姓名\t\t性别");
+               while (re.next()) {
+                   int id = re.getInt(1);
+                   String name = re.getString(2);
+                   String sex = re.getString(3);
+                   System.out.println(id+"\t\t"+name+"\t\t"+sex);
+               }
+               re.close();
+               st.close();
+               conn.close();
+           } catch (SQLException e) {
+               throw new RuntimeException(e);
+           }
+       }
+   
+   }
+   ```
+   
+   
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