Java 访问数据库

Java 访问数据库--删除

Java程序用于连接MySQL数据库并执行删除和更新操作。程序首先注册JDBC驱动，然后创建数据库连接。接着实例化Statement对象，执行SQL语句。最后，通过ResultSet对象查询并输出数据。

package com.cn;

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

public class update_Del {
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
String DB_URL = "jdbc:mysql://localhost:3306/student";
String user = "root";
String pass = "123456";
try {
// (1)注册 JDBC 驱动
Class.forName("com.mysql.cj.jdbc.Driver");
// (2)创建连接
conn = DriverManager.getConnection(DB_URL, user, pass);
// (3)实例化Statement对象，执行SQL语句
stmt = conn.createStatement();
String sql = "delete student where ID=1";
// String sql = "update student set Address='北京市海淀区' where ID=5";
int hasResultSet =stmt.executeUpdate(sql);

ResultSet rs = stmt.executeQuery("SELECT * FROM student");
System.out.print(" ID: " +"姓 名 " + "性别 "+"年龄 "+"系别 "+"地址 \n");
while (rs.next()) {
// （5）通过字段检索，进行查询操作
// 输出数据
System.out.print(" "+rs.getInt("ID"));
System.out.print(" "+rs.getString("Name"));
System.out.print(" "+rs.getString("Sex"));
System.out.print(" "+rs.getInt("Age"));
System.out.print(" "+rs.getString("dept"));
System.out.print(" "+rs.getString("Address"));
System.out.print("\n");
}
// （6）完成后关闭
rs.close();
stmt.close();
conn.close();
} catch (Exception e) {
System.out.print(e);
}
}

}

Java 访问数据库--查询

Java程序用于连接MySQL数据库并查询student1表中的数据。程序首先注册JDBC驱动，然后创建数据库连接。接着实例化Statement对象，执行SQL语句。最后，通过ResultSet对象查询并输出数据。

/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/

/**
*
* @author kai
*/
import java.sql.*;

public class DataBase {

public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
String DB_URL = "jdbc:mysql://localhost:3306/student";
String user = "root";
String pass = "789456";
try {
// (1)注册 JDBC 驱动
Class.forName("com.mysql.cj.jdbc.Driver");
// (2)创建连接
conn = DriverManager.getConnection(DB_URL, user, pass);
// (3)实例化Statement对象，执行SQL语句
stmt = conn.createStatement();
String sql = "SELECT * FROM student1";
ResultSet rs = stmt.executeQuery(sql);//(4)
while (rs.next()) {
// （5）通过字段检索，进行查询操作
int id = rs.getInt("ID");
String name = rs.getString("Name");
String sex = rs.getString("Sex");
// String address = rs.getString("Address");
// 输出数据
System.out.print("ID: " + id);
System.out.print(", 姓名: " + name);
System.out.print(", 性别: " + sex);
// System.out.print(", 地址: " + address);
System.out.print("\n");
}
// （6）完成后关闭
rs.close();
stmt.close();
conn.close();
} catch (Exception e) {
System.out.print(e);
}
}
}