Remove duplicate passenger train shifts, value interchange of two fields as duplicate values

Take out the recurring passenger train frequency

SELECT CID, From_city, to_city, Ticket_price
From city
WHERE CID in (SELECT DISTINCT first_value (CCID) through (PARTITION by from_city, To_city ORDER by from_city, to_city)
From (SELECT a.cid CCID,
A.from_city From_city,
A.to_city To_city,
A.ticket_price Price
From City A
UNION All
SELECT B.cid CCID,
B.to_city From_city,
B.from_city To_city,
B.ticket_price Price
From City B
ORDER by From_city, to_city))

CREATE TABLE City (CID number,from_city VARCHAR2, To_city VARCHAR2 (), ticket_price number)

INSERT into city (Cid,from_city,to_city,ticket_price)

SELECT,' Beijing ',' Shanghai ', from dual

UNION All

SELECT 02, ' Shanghai ', ' Shenzhen ', 280 from dual

UNION All

SELECT 03, ' Wuhan ', ' Guangzhou ', from dual

UNION All

SELECT 04, ' Xian ', ' Chengdu ', from dual

UNION All

SELECT 05, ' Shenzhen ', ' Shenzhen ', from dual

UNION All

SELECT,' Shanghai ',' Beijing ', from dual

UNION All

SELECT 07, ' Guangzhou ', ' Wuhan ', from dual

UNION All

SELECT 08, ' Shenzhen ', ' Shanghai ', 280 from dual

UNION All

SELECT 09, ' Chengdu ', ' Chongqing ', from dual

COMMIT;

Remove duplicate passenger train shifts, value interchange of two fields as duplicate values