How to order result by values IN() operator in SQL Server

Question

I want to order result of SELECT statement by values given within IN().

I have 200+ values within the IN operator.

Pseudo code:

select * 
from EmployeeId 
where EmployeeId in (2, 198, 5,...till 200)

Result set I am trying to achieve:

EmployeeId
----------    
     2
   198
     5
     .
     .
     .
   200

My research so far: when I use this, I cannot add square brackets ([]) within the IN operator.

Update: I am pasting values in in() operator from excel.

Thanks in advance.

Answer 1

2 things... 1) The IN operator doesn't provide any sorting capabilities. 2) Due to performance considerations, it's not a good idea to use more than a few values with the IN operator. The IN operator is evaluated as if were a series if OR conditions. So basically, it's the equivalent of writing out 200 Column = 2 OR column = 198... and so on.

Given your goal, I'd suggest using a #temp table. This will improve performance, allow you to sort and, if you assign the sorting column as the PK, you'll be able to sort the final result w/o having a sort operation in the execution plan of the final query (nice little bonus)...

IF OBJECT_ID('tempdb..#SearchValues', 'U') IS NOT NULL 
DROP TABLE #SearchValues;

CREATE TABLE #SearchValues (
    Sort INT NOT NULL IDENTITY(1,1) PRIMARY KEY CLUSTERED,
    Search INT NOT NULL 
    );
INSERT #SearchValues (Search) VALUES 
    (2),(198),(5),(75),(22),(300),(4),
    (122),(201),(40),(200);

SELECT 
    e.*
FROM
    dbo.Employee e
    JOIN #SearchValues sv
        ON e.EmployeeId = sv.Search
ORDER BY
    sv.Sort;

Answer 2

This is how conditional order by is done.

Order by 
case 
when EmployeeId = 2 then 1
when EmployeeId = 198 then 2
...
End

EDIT

Assuming you are taking in this comma separated string as a variable, or even if you are not you could store it as a variable, here is a smooth way by using a string splitter which would prevent you from having to manually create a temp table.

declare @table table(col1 int)

insert into @table
values
(1),
(2),
(3),
(4),
(5),
(6),
(7),
(8),
(9),
(10),
(11),
(12)

declare @searchVariable varchar (256) = '10,12,3,5,7,1'

select
    t.* 
from 
    @table t
cross apply
    dbo.DelimitedSplit8K (@searchVariable,',') s
where
    s.Item = t.col1
order by 
    s.ItemNumber    

The split function I used is from Jeff Moden and is added below. It's a good function to have as it is very performant compared to many other split functions.

CREATE FUNCTION [dbo].[DelimitedSplit8K] (@pString VARCHAR(8000), @pDelimiter CHAR(1))
--WARNING!!! DO NOT USE MAX DATA-TYPES HERE!  IT WILL KILL PERFORMANCE!

RETURNS TABLE WITH SCHEMABINDING AS
RETURN

/* "Inline" CTE Driven "Tally Table" produces values from 1 up to 10,000...
enough to cover VARCHAR(8000)*/

  WITH E1(N) AS (
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1
                ),                          --10E+1 or 10 rows
       E2(N) AS (SELECT 1 FROM E1 a, E1 b), --10E+2 or 100 rows
       E4(N) AS (SELECT 1 FROM E2 a, E2 b), --10E+4 or 10,000 rows max
 cteTally(N) AS (--==== This provides the "base" CTE and limits the number of rows right up front
                     -- for both a performance gain and prevention of accidental "overruns"
                 SELECT TOP (ISNULL(DATALENGTH(@pString),0)) ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) FROM E4
                ),
cteStart(N1) AS (--==== This returns N+1 (starting position of each "element" just once for each delimiter)
                 SELECT 1 UNION ALL
                 SELECT t.N+1 FROM cteTally t WHERE SUBSTRING(@pString,t.N,1) = @pDelimiter
                ),
cteLen(N1,L1) AS(--==== Return start and length (for use in substring)
                 SELECT s.N1,
                        ISNULL(NULLIF(CHARINDEX(@pDelimiter,@pString,s.N1),0)-s.N1,8000)
                   FROM cteStart s
                )
--===== Do the actual split. The ISNULL/NULLIF combo handles the length for the final element when no delimiter is found.
 SELECT ItemNumber = ROW_NUMBER() OVER(ORDER BY l.N1),
        Item       = SUBSTRING(@pString, l.N1, l.L1)
   FROM cteLen l
;
GO

Answer 3

I know it's a bit late but the best way would be

SELECT * 
FROM EmployeeId 
WHERE EmployeeId in (2, 198, 5,...till 200)
ORDER  BY CHARINDEX(CAST(EmployeeId AS VARCHAR), (2, 198, 5,...till 200))