Generate all combinations in SQL

Question

I need to generate all combinations of size @k in a given set of size @n. Can someone please review the following SQL and determine first if the fo

Answer 1

First create this UDF...

CREATE FUNCTION [dbo].[_ex_fn_SplitToTable] (@str varchar(5000), @sep char(1) = null)                           

RETURNS @ReturnVal table (n int, s varchar(5000))                           

AS                          
/*                          
Alpha Test                          
-----------                         
select * from [dbo].[_ex_fn_SplitToTable_test01]('abcde','')                            
*/                          

BEGIN                           
    declare @str2 varchar(5000)                     
    declare @sep2 char(1)                       
    if LEN(ISNULL(@sep,'')) = 0                     
    begin                       
        declare @i int                  
        set @i = 0                  

        set @str2 = ''                  
        declare @char varchar(1)                    
        startloop:                  
            set @i += 1             
            --print @i              
            set @char = substring(@str,@i,1)                
            set @str2 = @str2 + @char + ','             
            if LEN(@str) <= @i              
                goto exitloop           
            goto startloop              
        exitloop:                   
        set @str2 = left(@str2,LEN(@str2) - 1)                  
        set @sep2 = ','                 
        --print @str2                   

    end                         
    else                        
    begin                       
        set @str2 = @str                    
        set @sep2 = @sep                    
    end                     

    ;WITH Pieces(n, start, stop) AS (                           

      SELECT 1, 1, CHARINDEX(@sep2, @str2)                          

      UNION ALL                             

      SELECT n + 1, stop + 1, CHARINDEX(@sep2, @str2, stop + 1)                             

      FROM Pieces                           

      WHERE stop > 0                            

    )                           

    insert into @ReturnVal(n,s)                             
    SELECT n,                           
      SUBSTRING(@str2, start, CASE WHEN stop > 0 THEN stop-start ELSE 5000 END) AS s                            
    FROM Pieces option (maxrecursion 32767)                             


    RETURN                          

END                         



GO                          

Then create this stored proc...

CREATE proc [CombinationsOfString]                          
(                           
    @mystring varchar(max) = '0,5,10,15,20,25'                      
)                           
as                          

/*                          
ALPHA TEST                          
---------                           
exec CombinationsOfString '-20,-10,0,10,20'                         
*/                          
if object_id('tempdb..#_201606070947_myorig') is not null drop table #_201606070947_myorig                          

CREATE TABLE #_201606070947_myorig                          
 (                          
   SourceId  int      not null  identity(1,1)                           
  ,Element   varchar(100)  not null                         
 )                          
insert into #_201606070947_myorig                           
select s from dbo._ex_fn_SplitToTable(@mystring,',')                            

--select SourceId, Element from #_201606070947_myorig                           

declare @mynumerics varchar(max)                            

set @mynumerics = (                         
    select STUFF(REPLACE((SELECT '#!' + LTRIM(RTRIM(SourceId)) AS 'data()'                      
    FROM #_201606070947_myorig                      
    FOR XML PATH('')),' #!',', '), 1, 2, '') as Brands                      
)                           

set @mynumerics = REPLACE(@mynumerics,' ','')                           

print @mynumerics                           

if object_id('tempdb..#_201606070947_source') is not null drop table #_201606070947_source                          
if object_id('tempdb..#_201606070947_numbers') is not null drop table #_201606070947_numbers                            
if object_id('tempdb..#_201606070947_results') is not null drop table #_201606070947_results                            
if object_id('tempdb..#_201606070947_processed') is not null drop table #_201606070947_processed                            



CREATE TABLE #_201606070947_source                          
 (                          
   SourceId  int      not null  identity(1,1)                           
  ,Element   char(1)  not null                          
 )                          

--declare @mynumerics varchar(max)                          
--set @mynumerics = '1,2,3,4,5'                         
insert into #_201606070947_source                           
select s from dbo._ex_fn_SplitToTable(@mynumerics,',')                          

-- select * from #_201606070947_source                          

declare @Length int                         
set @Length = (select max(SourceId) from #_201606070947_source)                         
declare @columnstring varchar(max) = (SELECT REPLICATE('c.',@Length))                           
print @columnstring                         
declare @subs varchar(max) = (SELECT REPLICATE('substring.',@Length))                           
print @subs                         

if object_id('tempdb..#_201606070947_columns') is not null drop table #_201606070947_columns                            

select s+CONVERT(varchar,dbo.PadLeft(convert(varchar,n),'0',3)) cols                            
into #_201606070947_columns                         
from [dbo].[_ex_fn_SplitToTable](@columnstring,'.') where LEN(s) > 0                            

if object_id('tempdb..#_201606070947_subcolumns') is not null drop table #_201606070947_subcolumns                          
select s+'(Combo,'+CONVERT(varchar,n)+',1) ' + 'c'+CONVERT(varchar,dbo.PadLeft(convert(varchar,n),'0',3)) cols                          
into #_201606070947_subcolumns                          
from [dbo].[_ex_fn_SplitToTable](@subs,'.') where LEN(s) > 0                            

-- select * from #_201606070947_subcolumns                          
-- select * from #_201606070947_columns                         


declare @columns_sql varchar(max)                           
set @columns_sql =                          
        (                   
            select distinct                 
              stuff((SELECT distinct + cast(cols as varchar(50)) +  ' VARCHAR(1), '             
                       FROM (       
                        select cols 
                        from #_201606070947_columns     
                        ) t2    
                       --where t2.n = t1.n      
                       FOR XML PATH('')),3,0,'')        
            from (              
                select cols         
                from #_201606070947_columns             
                ) t1            
        )                   

declare @substring_sql varchar(max)                         
set @substring_sql =                            
        (                   
            select distinct                 
              stuff((SELECT distinct + cast(cols as varchar(100)) +  ', '               
                       FROM (       
                        select cols 
                        from #_201606070947_subcolumns  
                        ) t2    
                       --where t2.n = t1.n      
                       FOR XML PATH('')),3,0,'')        
            from (              
                select cols         
                from #_201606070947_subcolumns          
                ) t1            
        )                   
set @substring_sql = left(@substring_sql,LEN(@substring_sql) - 1)                           
print @substring_sql                            

set @columns_sql = LEFT(@columns_sql,LEN(@columns_sql) - 1)                         
--SELECT @columns_sql                           
declare @sql varchar(max)                           
set @sql = 'if object_id(''tempdb..##_201606070947_01'') is not null drop table ##_201606070947_01 create table ##_201606070947_01 (rowid int,' + @columns_sql + ')'                            
print @sql                          
execute(@sql)                           

CREATE TABLE #_201606070947_numbers (Number int not null)                           

insert into #_201606070947_numbers                          
select SourceId from #_201606070947_source                          

CREATE TABLE #_201606070947_results                         
 (                          
   Combo   varchar(10)  not null                            
  ,Length  int          not null                            
 )                          

 SET NOCOUNT on                         

DECLARE                         
  @Loop     int                         
 ,@MaxLoop  int                         


--  How many elements there are to process                          
SELECT @MaxLoop = max(SourceId)                         
 from #_201606070947_source                         


--  Initialize first value                          
TRUNCATE TABLE #_201606070947_results                           
INSERT #_201606070947_results (Combo, Length)                           
 select Element, 1                          
  from #_201606070947_source                            
  where SourceId = 1                            

SET @Loop = 2                           

--  Iterate to add each Element after the first                         
WHILE @Loop <= @MaxLoop                         
 BEGIN                          

    INSERT #_201606070947_results (Combo, Length)                       
     select distinct                        
        left(re.Combo, @Loop - nm.Number)                   
        + so.Element                    
        + RIGHT(re.Combo, nm.Number - 1)                    
       ,@Loop                       
      from #_201606070947_results re                        
       inner join #_201606070947_numbers nm                     
        on nm.Number <= @Loop                   
       inner join #_201606070947_source so                      
        on so.SourceId = @Loop                  
      where re.Length = @Loop - 1                       

    SET @Loop = @Loop + 1                       
 END                            
-- select * from #_201606070947_results                         
--  Show #_201606070947_results                         
SELECT *                            
into #_201606070947_processed                           
 from #_201606070947_results                            
 where Length = @MaxLoop                            
 order by Combo                         



-- select * from #_201606070947_processed                           
set @sql = 'if object_id(''tempdb..##_201606070947_02'') is not null drop table ##_201606070947_02 '                            
print @sql                          
execute(@sql)                           

set @sql = ' ' +                            
'  SELECT ROW_NUMBER() OVER(ORDER BY Combo Asc) AS RowID,' + @substring_sql +                           
'  into ##_201606070947_02 ' +                          
' FROM #_201606070947_processed ' +                         
' '                         
PRINT @sql                          
execute(@sql)                           

declare @columns_sql_new varchar(max)                           
set @columns_sql_new = REPLACE(@columns_sql,'(1)','(100)')                          
set @sql = 'if object_id(''tempdb..##_201606070947_03'') is not null drop table ##_201606070947_03 create table ##_201606070947_03 (RowId int,' + @columns_sql_new + ')'                            
PRINT @sql                          
execute(@sql)                           

insert into ##_201606070947_03 (RowId)                          
select RowId from ##_201606070947_02                            

--select * from ##_201606070947_03                          




DECLARE @ColumnId varchar(10)                           
DECLARE @getColumnId CURSOR                         
SET @getColumnId = CURSOR FOR                           
    select cols ColumnId from #_201606070947_columns                        
OPEN @getColumnId                           
FETCH NEXT                          
FROM @getColumnId INTO @ColumnId                            
WHILE @@FETCH_STATUS = 0                            
BEGIN                           
    PRINT @ColumnId                     
    set @sql = ' ' +                        
    ' update ##_201606070947_03                         
      set ' + @ColumnId + ' = B.Element                         
      from ##_201606070947_03 A                         
      , (                       

            select A.RowID, B.*             
            from                
            (               
                select * from ##_201606070947_02            
            ) A             
            ,               
            (               
                select * from #_201606070947_myorig         
            ) B             
            where A.' + @ColumnId + ' = B.SourceId              
        ) B                 
       where A.RowId = B.RowId                      
    '                       
    execute(@sql)                       
    print @sql                      

FETCH NEXT                          
FROM @getColumnId INTO @ColumnId                            
END                         
 CLOSE @getColumnId                         
DEALLOCATE @getColumnId                         

select * from ##_201606070947_03