用C++和MySQL写一个订餐管理系统

好的，订餐管理系统主要涉及到数据的增删改查以及用户界面的交互，下面是一个简单的实现：

首先，需要安装MySQL数据库和C++的MySQL驱动库。

1. 创建数据库和表格

在MySQL中创建名为“order_system”的数据库，然后在其中创建名为“orders”的表格，表格包括以下字段：

- id: 订单ID，自增长整数
- customer_name: 客户姓名，字符串
- dish_name: 菜品名称，字符串
- price: 菜品价格，浮点数
- order_time: 下单时间，日期时间类型

可以使用以下命令创建表格：

CREATE TABLE orders (
  id INT AUTO_INCREMENT PRIMARY KEY,
  customer_name VARCHAR(255) NOT NULL,
  dish_name VARCHAR(255) NOT NULL,
  price FLOAT NOT NULL,
  order_time DATETIME NOT NULL
);

2. C++代码实现

下面是一个简单的C++程序，实现了订餐管理系统的基本功能，包括添加订单、删除订单、查询订单和显示所有订单。

#include <iostream>
#include <mysql.h>

using namespace std;

// MySQL连接信息
const char* host = "localhost";
const char* user = "root";
const char* password = "123456";
const char* database = "order_system";

// 连接到MySQL
MYSQL* connect_to_mysql() {
    MYSQL* conn = mysql_init(NULL);
    if (!mysql_real_connect(conn, host, user, password, database, 0, NULL, 0)) {
        cerr << "Error connecting to database: " << mysql_error(conn) << endl;
        return NULL;
    }
    return conn;
}

// 添加订单
void add_order(MYSQL* conn) {
    string customer_name, dish_name;
    float price;
    cout << "Enter customer name: ";
    getline(cin, customer_name);
    cout << "Enter dish name: ";
    getline(cin, dish_name);
    cout << "Enter price: ";
    cin >> price;
    cin.ignore(); // 忽略换行符
    string query = "INSERT INTO orders (customer_name, dish_name, price, order_time) VALUES ('"
        + customer_name + "', '"
        + dish_name + "', "
        + to_string(price) + ", NOW())";
    if (mysql_query(conn, query.c_str())) {
        cerr << "Error adding order: " << mysql_error(conn) << endl;
    } else {
        cout << "Order added successfully." << endl;
    }
}

// 删除订单
void delete_order(MYSQL* conn) {
    int id;
    cout << "Enter order ID: ";
    cin >> id;
    cin.ignore(); // 忽略换行符
    string query = "DELETE FROM orders WHERE id = " + to_string(id);
    if (mysql_query(conn, query.c_str())) {
        cerr << "Error deleting order: " << mysql_error(conn) << endl;
    } else {
        cout << "Order deleted successfully." << endl;
    }
}

// 查询订单
void query_order(MYSQL* conn) {
    int id;
    cout << "Enter order ID: ";
    cin >> id;
    cin.ignore(); // 忽略换行符
    string query = "SELECT * FROM orders WHERE id = " + to_string(id);
    if (mysql_query(conn, query.c_str())) {
        cerr << "Error querying order: " << mysql_error(conn) << endl;
    } else {
        MYSQL_RES* res = mysql_store_result(conn);
        if (mysql_num_rows(res) == 0) {
            cout << "Order not found." << endl;
        } else {
            MYSQL_ROW row = mysql_fetch_row(res);
            cout << "ID: " << row[0] << endl;
            cout << "Customer name: " << row[1] << endl;
            cout << "Dish name: " << row[2] << endl;
            cout << "Price: " << row[3] << endl;
            cout << "Order time: " << row[4] << endl;
        }
        mysql_free_result(res);
    }
}

// 显示所有订单
void display_all_orders(MYSQL* conn) {
    string query = "SELECT * FROM orders";
    if (mysql_query(conn, query.c_str())) {
        cerr << "Error querying orders: " << mysql_error(conn) << endl;
    } else {
        MYSQL_RES* res = mysql_store_result(conn);
        int num_rows = mysql_num_rows(res);
        if (num_rows == 0) {
            cout << "No orders found." << endl;
        } else {
            MYSQL_ROW row;
            cout << "ID\tCustomer name\tDish name\tPrice\tOrder time" << endl;
            while ((row = mysql_fetch_row(res))) {
                cout << row[0] << "\t" << row[1] << "\t" << row[2] << "\t" << row[3] << "\t" << row[4] << endl;
            }
        }
        mysql_free_result(res);
    }
}

int main() {
    MYSQL* conn = connect_to_mysql();
    if (!conn) {
        return 1;
    }
    while (true) {
        cout << "1. Add order" << endl;
        cout << "2. Delete order" << endl;
        cout << "3. Query order" << endl;
        cout << "4. Display all orders" << endl;
        cout << "5. Quit" << endl;
        int choice;
        cout << "Enter your choice: ";
        cin >> choice;
        cin.ignore(); // 忽略换行符
        switch (choice) {
            case 1:
                add_order(conn);
                break;
            case 2:
                delete_order(conn);
                break;
            case 3:
                query_order(conn);
                break;
            case 4:
                display_all_orders(conn);
                break;
            case 5:
                mysql_close(conn);
                return 0;
            default:
                cout << "Invalid choice." << endl;
        }
        cout << endl;
    }
}

程序中使用了MySQL C API提供的函数进行数据库操作。在主函数中，使用一个无限循环来接受用户输入，根据用户的选择调用相应的函数。

3. 编译和运行

将以上代码保存到一个名为“order_system.cpp”的文件中，然后使用以下命令编译：

g++ -o order_system order_system.cpp `mysql_config --cflags --libs`

运行程序：

./order_system

程序会提示用户输入选项，根据提示进行操作即可。

注意：以上代码仅为演示用途，实际应用中需要考虑更多的异常情况和安全性问题。