#include <iostream>
#include <cstring>
#include <mariadb/conncpp.hpp>

// Delete a task record (indicated by id)
void deleteTask(std::unique_ptr<sql::Connection> &conn, int id) {
    try {
        // Create a new PreparedStatement
        std::unique_ptr<sql::PreparedStatement> stmnt(conn->prepareStatement("delete from tasks where id = ?"));
        // Bind values to SQL statement
        stmnt->setInt(1, id);
        // Execute query
        stmnt->executeQuery();
    }
    catch(sql::SQLException& e){
      std::cerr << "Error deleting task: " << e.what() << std::endl;
   }
}

// Update the completed value of a task record (indicated by id)
void updateTaskStatus(std::unique_ptr<sql::Connection> &conn, int id, bool completed) {
    try {
        // Create a new PreparedStatement
        std::unique_ptr<sql::PreparedStatement> stmnt(conn->prepareStatement("update tasks set completed = ? where id = ?"));
        // Bind values to SQL statement
        stmnt->setBoolean(1, completed);
        stmnt->setInt(2, id);
        // Execute query
        stmnt->executeQuery();
    }
    catch(sql::SQLException& e){
      std::cerr << "Error updating task status: " << e.what() << std::endl;
   }
}

// Create a new task record
void addTask(std::unique_ptr<sql::Connection> &conn, std::string description) {
    try {
        // Create a new PreparedStatement
        std::unique_ptr<sql::PreparedStatement> stmnt(conn->prepareStatement("insert into tasks (description) values (?)"));
        // Bind values to SQL statement
        stmnt->setString(1, description);
        // Execute query
        stmnt->executeQuery();
    }
    catch(sql::SQLException& e){
      std::cerr << "Error inserting new task: " << e.what() << std::endl;
   }
}

// Print all records in tasks table 
void showTasks(std::unique_ptr<sql::Connection> &conn) {
    try {
        // Create a new Statement
        std::unique_ptr<sql::Statement> stmnt(conn->createStatement());
        //or std::unique_ptr<sql::Statement> stmnt(coon->prepareStatement("select * from tasks where completed = ?");
        // stmnt->setBoolean(1, true);
        // Execute query
        sql::ResultSet *res = stmnt->executeQuery("select * from tasks");
        // Loop through and print results
        while (res->next()) {
            std::cout << "id = " << res->getInt(1);
            std::cout << ", description = " << res->getString(2);
            std::cout << ", completed = " << res->getBoolean(3) << "\n";
        }
    }
    catch(sql::SQLException& e){
      std::cerr << "Error selecting tasks: " << e.what() << std::endl;
   }
}

// Main Process
int main(int argc, char **argv){
    if (argc==1){
        std::cout << "Please provide an argument.\n";
    }
    else {
        try {
            // Instantiate Driver
            sql::Driver* driver = sql::mariadb::get_driver_instance(); 
            // Configure Connection
            sql::SQLString url("jdbc:mariadb://localhost:3306/todo");
            sql::Properties properties({{"user", "app_user"}, {"password", "Password123!"}});

            // Establish Connection
            std::unique_ptr<sql::Connection> conn(driver->connect(url, properties));
            //or replace the above statement with this
            // std::unique_ptr<sql::Conneciton> conn(sql::DriverManager::getConnection(url, props)

            // Use arguments to determine execution next steps
            if (!strcmp(argv[1],"showTasks")) {
                showTasks(conn);
            }
            else if (!strcmp(argv[1],"addTask")) {
                if (argc != 3) {
                    std::cout << "Invalid arguments";
                    return 1;
                }
                addTask(conn, argv[2]);
            }
            else if (!strcmp(argv[1],"updateTaskStatus")) {
                if (argc != 4) {
                    std::cout << "Invalid arguments";
                    return 1;
                }
                updateTaskStatus(conn, atoi(argv[2]), argv[3]);
            }
            else if (!strcmp(argv[1],"deleteTask")) {
                if (argc != 3) {
                    std::cout << "Invalid arguments";
                    return 1;
                }
                deleteTask(conn, atoi(argv[2]));
            }

            // Close Connection
            conn->close();
        }
        catch(sql::SQLException& e){
            std::cerr << "Error Connecting to MariaDB Platform: " << e.what() << std::endl;
            // Exit (Failed)
            return 1;
        }
    }

    // Exit (Success)
    return 0;
}

上面仅仅是示例代码，可以做如下优化：

1. 可以封装一个connection pool
2. 可以进一步的封装为一个数据库的访问模块，解耦mariadb/mysql部分和业务逻辑部分(sql)
3. 可以基于thread pool来drive db operation
4. ,