SQL 2005 Split Comma Separated Column on Delimiter

Question

My google searches on how to split a string on a delimiter have resulted in some useful functions for splitting strings when the string is known (i.e. see below):

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER FUNCTION [dbo].[Split] (@String varchar(8000), @Delimiter char(1))     
   returns @temptable TABLE (items varchar(8000))       
   as       
   begin       
       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)  
               insert into @temptable(Items) values(@slice)       

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

This works well for a known string like:

SELECT TOP 10 * FROM dbo.Split('This,Is,My,List',',')

However, I would like to pass a column to a function, and have it unioned together with my other data in it's own row... for example given the data:

CommaColumn   ValueColumn1   ValueColumn2
-----------   ------------   -------------
ABC,123       1              2
XYZ, 789      2              3

I would like to write something like:

SELECT Split(CommaColumn,',') As SplitValue, ValueColumn1, ValueColumn2 FROM MyTable

And get back

SplitValue    ValueColumn1   ValueColumn2
----------    ------------   ------------
ABC           1              2
123           1              2
XYZ           2              3
789           2              3

Is this possible, or has anyone done this before?

Answer 1

Yes, it's possible with CROSS APPLY (SQL 2005+):

with testdata (CommaColumn, ValueColumn1, ValueColumn2) as (
  select 'ABC,123', 1, 2 union all
  select 'XYZ, 789', 2, 3
  ) 
select 
  b.items as SplitValue
, a.ValueColumn1
, a.ValueColumn2
from testdata a
cross apply dbo.Split(a.CommaColumn,',') b

Notes:

1. You should add an index to the result set of your split column, so that it returns two columns, IndexNumber and Value.

2. In-line implementations with a numbers table are generally faster than your procedural version here.

eg:

create function [dbo].[Split] (@list nvarchar(max), @delimiter nchar(1) = N',')
returns table
as
return (
  select 
    Number = row_number() over (order by Number)
  , [Value] = ltrim(rtrim(convert(nvarchar(4000),
        substring(@list, Number
        , charindex(@delimiter, @list+@delimiter, Number)-Number
        )
    )))
  from dbo.Numbers
  where Number <= convert(int, len(@list))
    and substring(@delimiter + @list, Number, 1) = @delimiter
  )

Erland Sommarskog has the definitive page on this, I think: http://www.sommarskog.se/arrays-in-sql-2005.html