SQL Server select (top) two rows into two temp variables - sql-server

Question

I have a query which results in two or more rows (just one column) and I want to catch the first row value into first temp variable and second row value into second temp variable without using multiple times the select top 1 and select top 1 order by desc
Something like this;
Select row1 value into #tempvariable1, row2 value into #tempvariable2 from blah blah

Answer 1

You need somehow to identify the row (I am using a row ID in the example below, ordering by value - you can order by id or something else):
DECLARE #DataSource TABLE
(
[value] VARCHAR(12)
);
INSERT INTO #DataSource
VALUES ('value 1')
,('value 2')
,('value 3');
DECLARE #tempVariable1 VARCHAR(12)
,#tempVariable2 VARCHAR(12);
WITH DataSource ([value], [rowID]) AS
(
SELECT [value]
,ROW_NUMBER() OVER (ORDER BY [value])
FROM #DataSource
)
SELECT #tempVariable1 = IIF([rowID] = 1, [value], #tempVariable1)
,#tempVariable2 = IIF([rowID] = 2, [value], #tempVariable2)
FROM DataSource;
SELECT #tempVariable1
,#tempVariable2;

Answer 2

You can use a CTE where you will get the X values you need and then select from it:
declare #data table(id int);
insert into #data(id) values(8), (6), (4), (3);
with vals(id, n) as (
Select top(2) id, ROW_NUMBER() over(order by id)
From #data
)
Select #A = (Select id From vals Where n = 1)
, #B = (Select id From vals Where n = 2)
You could also use PIVOT:
Select #A = [1], #B = [2]
From (
Select id, ROW_NUMBER() over(order by id)
From #data
) v(id, n)
PIVOT (
max(id) FOR n in ([1], [2])
) as piv

Answer 3

You have two options
Let's say we test case is build as below
create table dbo.Test
(
value varchar(100) not null
)
GO
insert into dbo.Test
values
('A'),('B'),('NO THIS ONE'),('NO THIS ONE'),('NO THIS ONE')
GO
Now let's say you fetch your data as below
select t.value
from dbo.Test t
where t.value != 'NO THIS ONE'
GO
The first and easier option is to save the data in a temp table
declare #results as Table (value varchar(100))
insert into #results
select t.value
from dbo.Test t
where t.value != 'NO THIS ONE'
you still use TOP 1 BUT not in the entire data, only in the results.
Use TOP 1 to find the first result and a second TOP 1 where value is different from the first.
declare #A varchar(100), #B varchar(100)
set #A = (select top 1 r.value from #results r)
set #B = (select top 1 r.value from #results r where r.value != #A)
select #A, #B
GO
This approach have the advantage of performance.
Of course that don't work great if both values are equal. You can fix it by using a top 1 and ordering in the inverse order.
There's a better alternative using rownumber.
It works because if you set a variable when returning multiple rows the varible sticks with the last one (in fact it's reseted for each row iteration).
The case statement makes sure the variable #A is seted only on the first row iteration.
declare #A varchar(100), #B varchar(100)
/* This way #B receives the last value and #A the first */
select #B = t.value,
#A = (case when ROW_NUMBER() OVER(order by t.Value) = 1
then t.Value else #A
end)
from dbo.Test t
where t.value != 'NO THIS ONE'
select #A, #B