Group data irrespective of its presence in the separate columns - sql

Question

I have a table with different airline routes and I want to group them without taking into account which is the origin city and which is the destination.
e.g. the values of the routes Amsterdam-London and London-Amsterdam should be grouped together by the route Amsterdam-London.
Has anybody faced a similar problem?

Answer 1

I think you are looking for
CREATE TABLE Routes(
ID INT,
OriginalLocation VARCHAR(45),
Destination VARCHAR(45)
);
INSERT INTO Routes VALUES
(1, 'Amsterdam', 'London'),
(2, 'London', 'Amsterdam'),
(3, 'London', 'Algeria'),
(4, 'Algeria', 'France');
WITH C AS
(
SELECT *,
CASE WHEN EXISTS(
SELECT 1
FROM Routes
WHERE OriginalLocation = R.Destination --You can use UPPER()/LOWER() here
AND
Destination = R.OriginalLocation --and here too
AND
ID != R.ID
)
THEN ID
ELSE 0
END G
FROM Routes R
)
SELECT ID,
OriginalLocation,
Destination
FROM C
WHERE NOT (G > 1);
Returns:
+----+------------------+-------------+
| ID | OriginalLocation | Destination |
+----+------------------+-------------+
| 1 | Amsterdam | London |
| 3 | London | Algeria |
| 4 | Algeria | France |
+----+------------------+-------------+
Demo

Answer 2

In case you have table like
[flight routes]
originlocation| destinationlocation
Amsterdam | London
London | Amsterdam
You can try a set of sql queries like below
; with orderedroutes as
(
select distinct
originlocation= Case when originlocation < destinationlocation then originlocation else destinationlocation end ,
destinationlocation = Case when originlocation < destinationlocation then destinationlocation else originlocation end
from [flight routes]
)
select * from orderedroutes