Cout doesn't display all fields (C++, MySQL) - c++

Question

I have a function:
int main()
{
MySQL::Connect("127.0.0.1", 3306, "root", "", "player");
MySQL::ExecuteQuery("select * from player");
while (row = mysql_fetch_row(res))
{
std::cout << row[2] << "\n";
MySQL::SetDatabase("account");
MySQL::ExecuteQuery("select * from account"); // This function causes a problem.
// while (row = mysql_fetch_row(res))
// break;
}
return 0;
}
Which should get everything of player names from player table what it does and what it display in console (I'm posting a screenshot of table in Navicat):
https://i.stack.imgur.com/n6HJQ.png
However, when MySQL::ExecuteQuery("select * from account"); function is used which selects everything in account table, the earlier std::cout display only one player name instead of two:
https://i.stack.imgur.com/q9ZkP.png
What can I do in this situation? Or is there another simple way to connect to MySQL in C++? Please help.
I attach files such as MySQL_Func.cpp and MySQL_Func.h which include problematic function:
.cpp:
#include "MySQL_Func.h"
#include "../Log.hpp"
MYSQL* conn;
MYSQL_ROW row;
MYSQL_RES* res;
std::string conf_ip;
unsigned int conf_port;
std::string conf_db;
std::string conf_login;
std::string conf_password;
std::string error = mysql_error(conn);
int err = 0;
namespace MySQL
{
void Connect(std::string ip, unsigned int port, std::string login, std::string password, std::string db)
{
conf_ip = ip;
conf_port = port;
conf_login = login;
conf_password = password;
conf_db = db;
if (conn != 0)
{
SendLog(0, "MySQL has been restared.");
mysql_close(conn);
}
conn = mysql_init(0);
if (!mysql_real_connect(conn, ip.c_str(), login.c_str(), password.c_str(), db.c_str(), port, NULL, 0))
{
error = mysql_error(conn);
SendLog(1, "Connection with database was failed: " + error + ".");
exit(1);
}
else
{
SendLog(0, "Successfully connected with database!");
}
}
void ExecuteQuery(std::string query)
{
err = mysql_query(conn, query.c_str());
res = mysql_store_result(conn);
if (res != 0) // Protection against NullPointer.
{
int total_rows = mysql_num_fields(res);
if (total_rows != 0) // If total rows isn't 0.
{
if (err)
{
error = mysql_error(conn);
SendLog(1, "Query execute failed:" + error + ".");
mysql_free_result(res);
exit(1);
}
else
{
SendLog(0, "Query has been sent (" + query + ")!");
}
}
else
{
SendLog(1, "Query has been sent: (" + query + ") but its value is 0.");
exit(0);
}
}
else
{
exit(1);
}
}
void SetDatabase(std::string current_db)
{
if (current_db != conf_db) // If current_db isn't conf_db.
MySQL::Connect(conf_ip, conf_port, conf_login, conf_password, current_db);
}
}
.h:
#pragma once
#include <iostream>
#include <mysql.h>
#include <string>
extern MYSQL* conn;
extern MYSQL_ROW row;
extern MYSQL_RES* res;
extern std::string conf_ip;
extern unsigned int conf_port;
extern std::string conf_db;
extern std::string conf_login;
extern std::string conf_password;
namespace MySQL
{
void Connect(std::string ip, unsigned int port, std::string login, std::string password, std::string db);
void ExecuteQuery(std::string query);
void SetDatabase(std::string database);
}

Answer 1

Your two calls to ExecuteQuery share state, namely the "currently active query" and the buffered resultset you downloaded with mysql_result_row.
This is called a non-reentrant function.
Some options:
have a dedicated connection for each query
Do a single query that somehow combines the results (ie JOIN the players and accounts table)
Fetch all the players first into a dedicated datastructure (eg std::vector or std::map), then do the query for accounts later.