How to get first value from first row and last value from last row in SQL Server - sql

Question

I have a table in SQL Server as below
+---+-------------+-------------+-------------+
|Id | FromCity | ToCity | RequestId |
+---+-------------+-------------+-------------+
| 1 | Mysore | Atlanta | 12 |
+---+-------------+-------------+-------------+
| 2 | Atlanta | Singapore | 12 |
+---+-------------+-------------+-------------+
| 3 | Singapore | Pakistan | 12 |
+---+-------------+-------------+-------------+
| 4 | Pakistan | Myscot | 12 |
+---+-------------+-------------+-------------+
| 5 | Rome | Singapore | 13 |
+---+-------------+-------------+-------------+
Here, I am trying to get a value as From and To Cities (Round Trip Data) (i.e. Mysore - > Myscot for the RequestId =12). Ho to get this value?
When I pass RequestId=12, I should get the value as Mysore -> Myscot
I Tried as below:
SELECT MIN(FromCity) [From],
MAX(ToCity) [To]
FROM MyTable
WHERE RequestId = 12
But I'm getting Mysore -> Singapore (based on string MIN and MAX).

Answer 1

Check This :
SELECT M.FromCity [From],
M2.ToCity [To]
FROM #MyTable M
Inner join (select Min(ID) min ,Max(ID) max from #MyTable M2 WHERE M2.RequestId = 12 )
A on A.Min =ID
Inner join #MyTable M2 on M2.ID=A.Max
Output :

Answer 2

SELECT RequestId,
f.FromCity [From],
t.ToCity [To]
FROM MyTable t
CROSS APPLY (
SELECT TOP (1) FromCity
FROM MyTable
WHERE RequestId = t.RequestId
ORDER BY Id ASC
) f
CROSS APPLY (
SELECT TOP (1) ToCity
FROM MyTable
WHERE RequestId = t.RequestId
ORDER BY Id DESC
) t
WHERE RequestId = 12

Answer 3

The only logic I see is using the Id from your table and do something like this. Using CTE you will find the MIN and MAX id per request, that means from city - to city.
And after that you join your table to the CTE to find the actual values.
declare #tbl as table
([Id] int, [FromCity] varchar(9), [ToCity] varchar(9), [Date Created] datetime, [RequestId] int)
;
INSERT INTO #tbl
([Id], [FromCity], [ToCity], [Date Created], [RequestId])
VALUES
(1, 'Mysore', 'Atlanta', '2018-10-05 15:10:00', 12),
(2, 'Atlanta', 'Singapore', '2018-10-06 15:10:00', 12),
(3, 'Singapore', 'Pakistan', '2018-10-07 15:10:00', 12),
(4, 'Pakistan', 'Myscot', '2018-10-07 15:10:00', 12),
(5, 'UK', 'Atlanta', '2018-10-06 15:10:00', 13),
(6, 'Atlanta', 'Singapore', '2018-10-06 15:10:00', 13),
(7, 'Singapore', 'Italy', '2018-10-23 15:10:00', 13);
;with cte as (
select
MIN(Id) as [start]
,MAX(Id) as [end]
,RequestId
from #tbl
group by requestID
)
select
t1.FromCity
,t1.[Date Created]
,t2.ToCity
,t2.[Date Created]
from cte
inner join #tbl t1
on t1.Id = cte.[start]
and t1.RequestId = cte.RequestId
inner join #tbl t2
on t2.Id = cte.[end]
and t2.RequestId = cte.RequestId
Update: based on #Panagiotis Kanavos comment you can simplify the query like this
;with cte as (
select
MIN(Id) as [start]
,MAX(Id) as [end]
from #tbl
where RequestId = 12 ---> here you can use a variable containing the requestID
)
select
t1.FromCity
--,t1.[Date Created]
,t2.ToCity
--,t2.[Date Created]
from cte
inner join #tbl t1
on t1.Id = cte.[start]
inner join #tbl t2
on t2.Id = cte.[end]

Answer 4

If Id in main table is used to describe travel order then something like this will work:
SELECT startLocation.FromCity [From], endLocation.ToCity AS [To]
FROM (
SELECT MIN(Id) AS StartLocationId, MAX(Id) AS EndLocationId
FROM MyTable
WHERE RequestId = 12
) AS a
INNER JOIN MyTable AS startLocation ON a.StartLocationId = startLocation.Id
INNER JOIN MyTable AS endLocation ON a.EndLocationId = endLocation.Id
This is a example of solution for situation when ids are just ids and don`t match travel order:
declare #tbl as table
([Id] int, [FromCity] varchar(9), [ToCity] varchar(9), [Date Created] datetime, [RequestId] int)
;
INSERT INTO #tbl
([Id], [FromCity], [ToCity], [Date Created], [RequestId])
VALUES
(19, 'Mysore', 'Atlanta', '2018-10-05 15:10:00', 12),
(22, 'Atlanta', 'Singapore', '2018-10-06 15:10:00', 12),
(1, 'Singapore', 'Pakistan', '2018-10-07 15:10:00', 12),
(4, 'Pakistan', 'Myscot', '2018-10-07 15:10:00', 12),
(5, 'UK', 'Atlanta', '2018-10-06 15:10:00', 13),
(0, 'Atlanta', 'Singapore', '2018-10-06 15:10:00', 13),
(-1, 'Singapore', 'Italy', '2018-10-23 15:10:00', 13)
;
select * from #tbl
declare #Id int = 12
declare #FromStart nvarchar(255), #ToStart nvarchar(255)
declare #StartResult nvarchar(255), #ToResult nvarchar(255)
declare #StartResultFound bit = 0, #ToResultFound bit = 0
-- select random starting point
select #FromStart = [FromCity], #ToStart = [ToCity] from #tbl where [RequestId] = #Id
ORDER BY NEWID()
select #FromStart, #ToStart
while (#StartResultFound = 0)
begin
if exists (select top 1 1 from #tbl where [RequestId] = #Id and [ToCity] = #FromStart)
begin
select top 1 #FromStart = [FromCity] from #tbl where [RequestId] = #Id and [ToCity] = #FromStart
end
else
begin
set #StartResultFound = 1
set #StartResult = #FromStart
end
end
while (#ToResultFound = 0)
begin
if exists (select top 1 1 from #tbl where [RequestId] = #Id and [FromCity] = #ToStart)
begin
select top 1 #ToStart = [ToCity] from #tbl where [RequestId] = #Id and [FromCity] = #ToStart
end
else
begin
set #ToResultFound = 1
set #ToResult = #ToStart
end
end
select #StartResult, #ToResult

Answer 5

maybe this is whar you need
DECLARE
#t TABLE (
ID INT
, FromCity VARCHAR(250)
, ToCity VARCHAR(250)
, RequestId INT
)
INSERT INTO #t VALUES
(1,'Mysore','Atlanta',12)
,(2,'Atlanta','Singapore',12)
,(3,'Singapore','Pakistan',12)
,(4,'Pakistan','Myscot',12)
,(5,'Rome','Singapore',13)
SELECT DISTINCT
ISNULL(FromCity, ISNULL(NextCity, PreCity) ) FromCity
, ISNULL(ToCity, ISNULL(NextCity2, PreCity2) ) FromCity
FROM (
SELECT
CASE WHEN RN = 1 THEN FromCity END FromCity
, CASE WHEN RN = CNT THEN ToCity END ToCity
, LEAD(CASE WHEN RN = 1 THEN FromCity END) OVER(PARTITION BY RequestId ORDER BY ID) NextCity
, LEAD(CASE WHEN RN = CNT THEN ToCity END) OVER(PARTITION BY RequestId ORDER BY ID) NextCity2
, LAG(CASE WHEN RN = 1 THEN FromCity END) OVER(PARTITION BY RequestId ORDER BY ID) PreCity
, LAG(CASE WHEN RN = CNT THEN ToCity END) OVER(PARTITION BY RequestId ORDER BY ID) PreCity2
FROM (
SELECT
*, ROW_NUMBER() OVER(PARTITION BY RequestId ORDER BY ID) RN
, COUNT(ToCity) OVER(PARTITION BY RequestId) CNT
FROM #t
) D
WHERE
RN = 1 OR RN = CNT
) C

Answer 6

A recursive version, not depending on Ids order. The idea is to build the biggest chain of trip connected by To / From cities.
WITH cte1 AS (
-- start with all trips as 1 hop chain
SELECT [FromCity], [ToCity], 1 AS HOP
FROM Mytable
WHERE REQUESTID = 12
UNION ALL
-- recursively add one hop if we find a trip ending in start city of the chain
SELECT T.[FromCity], cte1.[ToCity], cte1.HOP + 1
FROM cte1
JOIN Mytable t
ON t.[ToCity] = cte1.[FromCity]
WHERE t.REQUESTID = 12
)
, cte2 AS (
-- order by number of hops
SELECT [FromCity], [ToCity], ROW_NUMBER() OVER (ORDER BY HOP DESC) AS N
FROM cte1
)
-- choose the chain with the more hops
SELECT [FromCity], [ToCity]
FROM cte2
WHERE N = 1

Answer 7

try this code
SELECT MIN(Id) [From],
MAX(Id) [To]
FROM MyTable
WHERE RequestId = 12