Demande d'aide c++ et requête SQL

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <winsock.h>
#include <MYSQL/mysql.h>
#include "connexion.h"

using namespace std;

int main(){


  char *hostname,*user,*password,nombase[50];
  unsigned int port;
  hostname="localhost";
  user="root";
  password="012345";
  port=3309;
  strcpy_s(nombase,"test");
  Connexion C(hostname,user,password,port);//instanciation de la classe connexion avec les parametres de la base
  ;

  
if(C.connect("test")==true)
	{
	system("cls");
	cout<<"\n";
	cout<<"\t        ************************************************          \n";
	cout<<"\t        *                                              *          \n";
	cout<<"\t        *  veuillez patienter pendant le chargement    *          \n";
	cout<<"\t        *                                              *          \n";
	cout<<"\t        ************************************************          \n";
	cout<<"\n";
	for(int i=0;i<1;i++)
	cout<<"\n";
	cout<<"\n";
	cout<<"\n";
	cout<<"\n\t\t */*\\/*\\/*\\OUVERTURE DE L'APPLICATION/*\\/*\\/*\\*         \n"; 
	cout<<"\n";	
	cout<<"\n\n\n\t\tChargement";
		for(int j=1;j<40;j++)
		{
			Sleep(100);//attente
				cout<<".";
		}
	system("cls");
		
	mysql_query(C.mysql, "SELECT * FROM client;");
            MYSQL_ROW row;
            MYSQL_RES *result;
			result = mysql_store_result(C.mysql);
			char nrows= mysql_num_fields(result);

			while (row = mysql_fetch_row(result))
			{
				
				for ( int i=0; i < nrows; i++) 
				{
		   

					cout<<row[i]<<"\t";
				}
				
				cout<<endl;
			}

			mysql_free_result(result);

	
			
    
	}
	else
	{
	  cout<<"echec de Connexion avec la base";
	  system("pause");
	  return -1;
	}

	

		cout<<"\n";
	    cout<<"\n"; 
	C.deconnect();
	system("pause");
	return 0;
	
	

}

cout<<"\n";
cout<<"\t        ************************************************          \n";
cout<<"\t        *                                              *          \n";
cout<<"\t        *  veuillez patienter pendant le chargement    *          \n";
cout<<"\t        *                                              *          \n";
cout<<"\t        ************************************************          \n";

std::cout <<
 <<"\n\t        ************************************************          \n"
 <<"\t        *                                              *          \n"
 <<"\t        *  veuillez patienter pendant le chargement    *          \n"
 <<"\t        *                                              *          \n"
 <<"\t        ************************************************          " << std::endl;

// Pensez à inclure <sstream>
int a;
std::cout << "donner age" << std::endl;
std::cin >> a;
std::ostringstream query;
query << "SELECT * FROM client where age= " << a << ";";
mysql_query(C.mysql, query.str().c_str());