with update_table as (
select 
a.item_code as CODE,
a.item_name as NAME,
'UPDATED' as COMP_RSLT
from
item a
inner join item_history b
on a.item_code = b.item_code
where 
a.item_code = b.item_code
and a.user_update_datetime > b.user_update_datetime
)
,delete_table as (
select 
a.item_code as CODE,
a.item_name as NAME,
'DELETED' as COMP_RSLT
from
item_history a
left outer join item b
on a.item_code = b.item_code
where b.item_code is null

)
,add_table as (
select 
a.item_code as CODE,
a.item_name as NAME,
'ADDED' as COMP_RSLT
from
item a
left join item_history b
on a.item_code = b.item_code
where 
 b.item_code is null
)
select CODE, NAME, COMP_RSLT from update_table
union all
select CODE, NAME, COMP_RSLT from add_table
union all
select CODE, NAME, COMP_RSLT from delete_table
order by CODE desc
;