This time, we're traveling between cities (table
german_city with columns:
name) in Germany and we don't calculate the distance using a gps function. Instead, you are given a second table called
time) with average trip durations on a given route from one city to another.
Let's travel between the four cities starting in Berlin. Your task is to list the travel paths starting in Berlin and covering all four cities. Order the paths in descending order by
In your answer, provide the following columns:
path – city names separated by
last_id – ID of the last city,
total_time – total time spent driving,
count_places – the number of places visited, should equal 4.
This one can be tough, so here is a hint: in the recursive member, you will have to join the recursive table you create with the table
road, and the table
german_city twice (one
city_from, the other one for
city_to). In the termination check, use
position(x IN path) = 0 to make sure that city x has not been visited so far.