Check record exists by splitting particular column value in SQL Server

Hi Team,

In User table, assigning markets to all users with their market id's. Now while checking, market exists for particular user it not returning any rows.

User Market test 1,2 test1 3,4 test3 5,6

For spliiting market column used below function.

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

and if we use the below sql statement, it not returning any rows.

select * from userlist where Userid in (test) and Market  in  (select items from dbo.Split('5,28,1',','))

Kindly help me on this.

Thank you