SQL Server: Split Function

create FUNCTION Split(@String varchar(MAX), @Delimiter char(1))       
returns @temptable TABLE (items varchar(MAX))       
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;

select items, count(items)
from table1 t1
cross apply dbo.split(t1.id, ‘,’)
group by items

Source: http://stackoverflow.com/questions/12920013/t-sql-split-and-aggregate-comma-separated-values?rq=1