if object_id('[BOM]') is not null drop table [BOM]
go
create table [BOM] (CO_CD int,ITEMPARENT_CD nvarchar(40),BOM_SQ int,CHILD_CD nvarchar(40),QTY int)
insert into [BOM]
select 1000,'10C-AD-AT-NAC11-P',1,'A30C-SAN0752N01-(14)',1 union all
select 1000,'10C-AD-AT-NAC11-P',2,'A055-CA2AUS-L',1 union all
select 1000,'10C-AD-AT-NAC11-P',3,'A061-AD-AT-NAC11-L',1 union all
select 1000,'10C-AD-AT-NAC11-P',4,'A061-AD-AT-NAC11-IBL',1 union all
select 1000,'10C-AD-AT-NAC11-P',5,'A068-AD-00-AC-1620',1 union all
select 1000,'A30C-SAN0752N01-(14)',1,'A056-AD-00-AC-1620',1 union all
select 1000,'A30C-SAN0752N01-(14)',2,'A054-AD-00-AC-1620',1 union all
select 1000,'A30C-SAN0752N01-(14)',3,'A053-AD-00-AC-1620',1 union all
select 1000,'A30C-SAN0752N01-(14)',4,'A052-AD-00-AC-1620',1 union all
select 1000,'A30C-SAN0752N01-(14)',5,'A051-AD-00-AC-1620',1

if object_id('[mono]') is not null drop table [mono]
go
create table [mono] (CO_CD int,ITEM_CD nvarchar(40),ITEM_NM nvarchar(6))
insert into [mono]
select 1000,'10C-AD-AT-NAC11-P','AAA' union all
select 1000,'A30C-SAN0752N01-(14)','BBB'

select * from [BOM]
select * from [mono]


declare @i nvarchar(50)
set @i ='10C-AD-AT-NAC11-P';

with PCTE
as(
select 1 as lvl,bom_sq,CHILD_CD ,QTY
from BOM 
where ITEMPARENT_CD = @i
union all
select PCTE.lvl +1,N.bom_sq,N.CHILD_CD,PCTE.QTY*N.QTY as qty
from PCTE inner join BOM as N
on PCTE.child_cd = N.ITEMPARENT_CD)

select * from PCTE

/*
lvl         bom_sq      CHILD_CD                                 QTY
----------- ----------- ---------------------------------------- -----------
1           1           A30C-SAN0752N01-(14)                     1
1           2           A055-CA2AUS-L                            1
1           3           A061-AD-AT-NAC11-L                       1
1           4           A061-AD-AT-NAC11-IBL                     1
1           5           A068-AD-00-AC-1620                       1
2           1           A056-AD-00-AC-1620                       1
2           2           A054-AD-00-AC-1620                       1
2           3           A053-AD-00-AC-1620                       1
2           4           A052-AD-00-AC-1620                       1
2           5           A051-