ER图

#include #include se>#include #include #include #include #include #include #include using namespace std;class birthday{private:    int year_;    int month_;    int day_;public:    birthday(){}    birthday(int x,int y,int z)    {        year_ = x;        month_ = y;        day_ = z;    }    int get_year()    {        return year_;    }    friend ostream &operator<<(ostream &os, const birthday &item)    {        os<< item.year_<<"-"<>(istream &is, birthday &item)    {        is>> item.year_>> item.month_>>item.day_;        return is;    }    QString toString()//转化为QString类型用来导入数据库    {        QString s;        s= year_+ '-' + month_+ '-' + day_;        return s;    }    string toStdString()    {        string s;        s= year_+'-'+month_+'-'+day_;        cout<se>