Recursive Query - Bills of Materials

Question

I have a table that list all Parts that have materials (PartMtl table).  Ex. part 1 has materials 2a, 2b, & 2c.  I tie this table to a PartCost table linked on the materials.  So I get costs for 2a, 2b, & 2c.  This works smooth.  Now when I want to go a level deeper, and get 2a's materials, 3a, & 3b.  things get a little more complicated.  Up until this point, I have simply created aliases for the PartMtl & PartCost tables. 
The problem with this method is I need to build the report with an alias for each table for each level for as many levels as I imagine our materials listings can grow.  This design is shaky at best and does not allow for additional levels.  Is there a way to dynamically create this recursion? 
Thank you,

Answer 1

You can base the report on an SQL Command something like (MS SQL):
declare @level int;
declare @reccnt int;
declare @reccnt2 int;
set @level = 1;
select @level as level,
  pm.parent,
  pm.component,
  pm.qty_required,
  pc.cost
into #temp
from PartMtl pm, PartCost pc
where pm.parent = '{?item to explode}'
and pm.component = pc.part_id;
set @reccnt = 0;
set @reccnt2 = ( select count(*) from #temp );
/* loop until no more records inserted */
while @reccnt <> @reccnt2
begin
  set @level = @level + 1;
  insert into #temp
  select @level as level,
    pm.parent,
    pm.component,
    pm.qty_required,
    pc.cost
  from #temp t, PartMtl pm, PartCost pc
  where t.level = @level - 1
  and t.component = pm.parent
  and pm.component = pc.part_id
  set @reccnt = @reccnt2;
  set @reccnt2 = ( select count(*) from #temp );
end;
HTH,
Carl