1using System;
2using System.Data;
3using System.Data.SQLite;
4
5class Program
6{
7    static void Main()
8    {
9        string connectionString = "Data Source=your_database.db;Version=3;";
10        using (SQLiteConnection connection = new SQLiteConnection(connectionString))
11        {
12            connection.Open();
13
14            string query = "SELECT customer_id, COUNT(visit_id) AS count_no_trans FROM Visits LEFT JOIN Transactions ON Visits.visit_id = Transactions.visit_id WHERE Transactions.transaction_id IS NULL GROUP BY customer_id;";
15            using (SQLiteCommand command = new SQLiteCommand(query, connection))
16            {
17                using (SQLiteDataReader reader = command.ExecuteReader())
18                {
19                    while (reader.Read())
20                    {
21                        Console.WriteLine($"customer_id: {reader["customer_id"]}, count_no_trans: {reader["count_no_trans"]}");
22                    }
23                }
24            }
25        }
26    }
27}

#include <iostream>
#include <string>
#include <sqlite3.h>

void executeSQL(const std::string &query) {
    sqlite3 *db;
    char *zErrMsg = nullptr;
    int rc;

    rc = sqlite3_open("your_database.db", &db);
    if(rc) {
        std::cerr << "Can't open database: " << sqlite3_errmsg(db) << std::endl;
        return;
    }

    rc = sqlite3_exec(db, query.c_str(), callback, 0, &zErrMsg);
    if(rc != SQLITE_OK) {
        std::cerr << "SQL error: " << zErrMsg << std::endl;
        sqlite3_free(zErrMsg);
    }
    sqlite3_close(db);
}

int main() {
    std::string query = "SELECT customer_id, COUNT(visit_id) AS count_no_trans FROM Visits WHERE NOT EXISTS (SELECT * FROM Transactions WHERE Visits.visit_id = Transactions.visit_id) GROUP BY customer_id;";
    executeSQL(query);
    return 0;
}

// Note: Make sure to implement the callback function and handle the database initialization and cleanup properly. The query provided is SQL and should be run on a SQL-compliant database like SQLite3.