如何将多列连接为多列？

Question

我有一个trip表，其中包含from_city和to_city列，其中包含city表的外键。

如何使用以city作为主键的id表进行联接，以便获得具有from_city_name和to_city_name的结果联接表？

Answer 1

进行两次内部联接，如下所示。有关SQL连接的更多信息，请参见MySQL Join Made Easy For Beginners

#include <iostream>

using namespace std;

int main()
{

enum days { Sun, Mon, Tue, Wed, Thu,Fri,Sat };
int day;
cout << " Enter a day ";
cin >> day;

switch (day)
{
case 0:
    cout << "Weekend" << endl;
    break;

case 1:
    cout << "Start of work week " << endl;
    break;

case 2:
    cout << "Midweek" << endl;
    break;

case 3:
    cout << "Midweek" << endl;
    break;

case 4:
    cout << "Midweek" << endl;
    break;

case 5:
    cout << "End of work  week" << endl;
    break;

case 6:
    cout << "Weekend" << endl;
    break;

default:
   cout << "Invalid day of the week" << endl;
    return 0;

}
}