Sql-server – select distinct on csv data

csvdistinctselectsql serversql-server-2008-r2

A table has CSV data and I want to do a SELECT DISTINCT ID on that table, how should I proceed?

+-----------+
| id        |
+-----------+
| 111,1487  |
+-----------+
| 462       |
+-----------+
| 2492      |
+-----------+
| 3184      |
+-----------+
| 3181,3184 |
+-----------+
| 3181      |
+-----------+
| 440       |
+-----------+
| 1436      |
+-----------+

I've got a function which I usually use that can split varchar csv string of INTs into a one-column table which I use as follow:

SELECT number from INTLIST_TO_TBL('123,234,345,4566')

It works well but I can't use it in this case as there are many rows and it will return multiple rows in certain cases.

Should I try using a cursor that inserts into a temporary table then proceed to the next step by querying this temporary table ?

I've been told cursors are synonym of poor performance which is why I always resort to asking here first before going down that road.

Best Answer

You should be able to use CROSS APPLY.

In an effort to provide a Minimum Complete Verifiable Example, I've included a 'simple' SPLIT TVF which is intended to emulate your INTLIST_TO_TBL function. This is for demonstration purposes only and there are more efficient ways to split a string that are beyond my answer.

IF EXISTS ( SELECT  *
            FROM    sys.objects
            WHERE   object_id = OBJECT_ID(N'[dbo].[Split]')
                    AND type IN (N'FN', N'IF', N'TF', N'FS', N'FT') ) 
    DROP FUNCTION [dbo].[Split] ;
GO
CREATE FUNCTION [dbo].[Split](@String varchar(8000), @Delimiter char(1))        
returns @temptable TABLE (element int,items varchar(8000))        
as        
begin        
    declare @element int=1
    declare @idx int        
    declare @slice varchar(8000)        

    select @idx = 1        
        if len(@String)<1 or @String is null  return        

    while @idx!= 0        
    begin        
        set @idx = charindex(@Delimiter,@String)        
        if @idx!=0        
            set @slice = left(@String,@idx - 1)        
        else        
            set @slice = @String        

        if(len(@slice)>0)
            begin   
                insert into @temptable(Element,Items) values(@element,@slice)        
                set @element=@element+1
            end 

        set @String = right(@String,len(@String) - @idx)        
        if len(@String) = 0 break        
    end    
return        
end


GO

Now that we have the Split TVF, let's see an example of how to incorporate it.

DECLARE @tbl TABLE (id VARCHAR(100))

INSERT @tbl
VALUES ('111,1487')
    ,('462')
    ,('2492')
    ,('3184')
    ,('3181,3184')
    ,('3181')
    ,('440')
    ,('1436')

SELECT DISTINCT b.items
FROM @tbl a
CROSS APPLY [dbo].[Split](a.id, ',') b
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