CREATE TABLE #Trips(
  Origin VARCHAR(50)
 ,Destination VARCHAR(50)
 ,Tonnage FLOAT
);

INSERT INTO #Trips(Origin, Destination, Tonnage)
VALUES
  ('Alabama', 'Arizona',  0.0012),
  ('Alabama', 'Idaho',    1.2),
  ('Idaho',   'Alaska',   644),
  ('Arizona', 'Alaska',   665),
  ('Arizona', 'Alabama',  788),
  ('Alabama', 'Texas',    12),
  ('Idaho',   'Alabama',  666),
  ('Alaska',  'Idaho',    456),
  ('Alaska',  'Idaho',    0),
  ('Arizona', 'Michigan', 0)


SELECT * FROM #Trips;



DROP TABLE #Trips;

USE [TEMPDB]   -- safe place
GO

--  go and create some test data to play with

IF  EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[Location]') AND type in (N'U'))
DROP TABLE [dbo].[Location]
GO

CREATE TABLE [dbo].[Location](
	[LocationID] [varchar](1) NULL
) ON [PRIMARY]

GO

INSERT INTO [dbo].[Location]([LocationID])
SELECT N'A' UNION ALL
SELECT N'B' UNION ALL
SELECT N'C' UNION ALL
SELECT N'D' UNION ALL
SELECT N'E'

IF  EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[Trips]') AND type in (N'U'))
DROP TABLE [dbo].[Trips]
GO


CREATE TABLE [dbo].[Trips](
	[Origin] [varchar](1) NULL,
	[Destnation] [varchar](1) NULL,
	[Tonnage] [int] NULL
) ON [PRIMARY]

GO

INSERT INTO [dbo].[Trips]([Origin], [Destnation], [Tonnage])
SELECT N'A', N'B', 5 UNION ALL
SELECT N'A', N'D', 2 UNION ALL
SELECT N'B', N'A', 3 UNION ALL
SELECT N'B', N'E', 7 UNION ALL
SELECT N'B', N'A', 5 UNION ALL
SELECT N'B', N'D', 2 UNION ALL
SELECT N'C', N'A', 1 UNION ALL
SELECT N'C', N'A', 18 UNION ALL
SELECT N'D', N'C', 12 UNION ALL
SELECT N'D', N'A', 5 UNION ALL
SELECT N'D', N'E', 6 UNION ALL
SELECT N'A', N'B', 12 UNION ALL
SELECT N'D', N'C', 30 UNION ALL
SELECT N'E', N'D', 100 UNION ALL
SELECT N'D', N'E', 50 UNION ALL
SELECT N'E', N'C', 12 UNION ALL
SELECT N'E', N'A', 15

--do some work to start playing with

;WITH cte AS 
(
SELECT A.LocationID AS Origin , 
       B.LocationID AS Destination
  FROM
       Location A INNER JOIN Location B ON A.LocationID <> B.LocationID
       
)       
       
SELECT CTE.Origin, CTE.Destination, SUM(COALESCE (Trips.Tonnage, 0)) AS TOTALS
FROM  CTE LEFT OUTER JOIN
               Trips ON CTE.Destination = Trips.Destnation AND CTE.Origin = Trips.Origin
GROUP BY CTE.Origin, CTE.Destination
HAVING (SUM(COALESCE (Trips.Tonnage, 0)) > 0)
ORDER BY CTE.Origin, CTE.Destination

CREATE TABLE #Trips(
  Origin VARCHAR(50)
 ,Destination VARCHAR(50)
 ,Tonnage FLOAT
);

INSERT INTO #Trips(Origin, Destination, Tonnage)
VALUES
  ('Alabama', 'Arizona',  0.0012),
  ('Alabama', 'Idaho',    1.2),
  ('Idaho',   'Alaska',   644),
  ('Arizona', 'Alaska',   665),
  ('Arizona', 'Alabama',  788),
  ('Alabama', 'Texas',    12),
  ('Idaho',   'Alabama',  666),
  ('Alaska',  'Idaho',    456),
  ('Alaska',  'Idaho',    0),
  ('Arizona', 'Michigan', 0)

CREATE TABLE #Trips1(
  Origin VARCHAR(50)
 ,Destination VARCHAR(50)
 ,Tonnage FLOAT
);

declare @originA varchar(50),@DestinationA varchar(50),@originB varchar(50),@destinationB varchar(50),
@tonnageA float,@tonnageB float

declare trip_cursor cursor for
 
SELECT distinct  a.origin as originA ,
a.destination As destinationA,
a.tonnage As tonnageA,
b.origin as originB,
b.destination as destinationB,
b.tonnage as tonnageB FROM #Trips a
outer apply #trips b
where a.Origin=b.Destination
and a.Destination=b.Origin
and a.tonnage<>0
and b.tonnage<>0

open trip_cursor

fetch next from trip_cursor into 
@originA ,@DestinationA ,@tonnageA,@originB ,@destinationB 
 ,@tonnageB 
while @@FETCH_STATUS=0
begin
insert into #Trips1 values (@originA,@DestinationA,@tonnageA)

insert into #Trips1 values (@originB,@DestinationB,@tonnageB)

fetch next from trip_cursor into 
@originA ,@DestinationA ,@tonnageA,@originB ,@destinationB 
 ,@tonnageB 
end

close trip_cursor
deallocate trip_cursor
insert into #Trips1 (origin,destination,tonnage) select origin,destination,tonnage from #Trips where Tonnage<>0
except select origin,destination,tonnage from #Trips1-- where tonnage <>0
select   * from #Trips1
drop table #Trips1

CREATE TABLE #Trips
    (Origin VARCHAR(50), Destination VARCHAR(50), Tonnage FLOAT);

INSERT INTO #Trips(Origin, Destination, Tonnage)
VALUES
  ('Alabama', 'Arizona',  0.0012),
  ('Alabama', 'Idaho',    1.2),
  ('Alabama', 'Alaska',    12),
  ('Idaho',   'Alaska',   644),
  ('Idaho',   'Alabama',  666),
  ('Idaho',   'Arizona',    667),
  ('Arizona', 'Alaska',   665),
  ('Arizona', 'Alabama',  788),
  ('Arizona', 'Idaho',    588),
  ('Alaska',  'Idaho',    456),
  ('Alaska',  'Arizona',    0),
  ('Alaska',  'Alabama',    0)

;WITH CTE AS (
    SELECT c.Origin, c.Destination, c.Tonnage
        ,n=ROW_NUMBER() OVER (ORDER BY (SELECT NULL))
    FROM #Trips a
    CROSS APPLY #Trips b
    CROSS APPLY (
        VALUES (a.Origin, a.Destination, a.Tonnage)
            ,(b.Origin, b.Destination, b.Tonnage)) c(Origin, Destination, Tonnage)
    WHERE (a.Origin = b.Destination AND b.Origin = a.Destination))
SELECT Origin, Destination, Tonnage
FROM (
    SELECT Origin, Destination, Tonnage
    FROM CTE a
    WHERE EXISTS (
        SELECT 1 
        FROM CTE b 
        WHERE b.n < a.n AND b.Origin = a.Origin AND b.Destination = a.Destination)) b 
--WHERE Tonnage <> 0
 
DROP TABLE #Trips

Origin	Destination	Tonnage
Idaho	Alabama		666
Alabama	Idaho		1.2
Arizona	Alabama		788
Alabama	Arizona		0.0012
Arizona	Idaho		588
Idaho	Arizona		667
Alaska	Idaho		456
Idaho	Alaska		644
Alaska	Arizona		0
Arizona	Alaska		665
Alaska	Alabama		0
Alabama	Alaska		12