Circular dependency expected class-name before '{' token - c++

Question

sorry in advance to start another one of those circular dependency threads but I tried almost everything and maybe a fresh pair of eyes can help.
How do I get this * compiled?
CARD.H
#ifndef CARD_H
#define CARD_H
#include <string>
#include <sstream>
#include <irrKlang.h>
#include "Database.h"
using namespace std;
using namespace irrklang;
class Card: public Database{ // problem expected class-name before '{' token
public:
DATABASE.H
#ifndef __DATABASE_H__
#define __DATABASE_H__
#include <string>
#include <vector>
#include <sqlite3.h>
#include <wx/string.h>
#include <irrKlang.h>
#include <wx/file.h>
#include "Card.h" // even though i include card.h
using namespace std;
using namespace irrklang;
class Card; // if i take this out, I get: 'Card' was not declared in this scope|
class Database
{
public:
vector<Card> queryC(wstring query);

Answer 1

Two rules to help prevent circular dependencies:
1.) If you don't need the implementation of a class, declare it by forward reference only.
2.) If you need the implementation, include the header file as late as possible.
Card.h
#ifndef CARD_H
#define CARD_H
#include "Database.h"
class Card : public Database {
public:
int card;
};
#endif // #ifndef CARD_H
Database.h
#ifndef DATABASE_H
#define DATABASE_H
#include <vector>
#include <string>
class Card;
class Database {
public:
std::vector<Card> queryC(std::string query);
};
#endif // #ifndef DATABASE_H
Card.cpp
#include "Card.h"
Card card;
Database.cpp
#include "Database.h"
Database database;
.
$ g++ -c Card.cpp -o Card.o
$ g++ -c Database.cpp -o Database.o
$ ls -l Card.o Database.o
-rw-r--r-- 1 user group 959 19. Sep 09:13 Card.o
-rw-r--r-- 1 user group 967 19. Sep 09:13 Database.o