Question

I need to be able to calculate the minimum distance between two cities given a table that has the distances between pairs of cities. Two cities may not be connected directly, instead they may be connected via a third city and so on.

Here are the tables that I have

SQL> desc city
 Name                                      Null?    Type
 ----------------------------------------- -------- ------------

 CITY_ID                                   NOT NULL NUMBER
 CITY_NAME                                 NOT NULL VARCHAR2(80)
 CITY_STATE                                         VARCHAR2(80)
 ACTIVE                                             CHAR(1)

and

SQL> desc connection
 Name                                      Null?    Type
 ----------------------------------------- -------- -------

 CITY1                                     NOT NULL NUMBER
 CITY2                                     NOT NULL NUMBER
 NO_OF_DAYS                                NOT NULL NUMBER

I don’t know how recursion and backtracking work in pl/sql.

Answer 1

You could try coding Dijkstra’s algorithm in PL/SQL.

Or try this SQL solution.