create table #HOLD (
   ...
   property      varchar(50),
   ...
   record_state  char(1)
)

##</code><code>##

-- (a) Report new values
select distinct property 
from #HOLD
where property not in (select property from table2)

-- (b) Mark records containing those new values
update #HOLD set record_state='N'
where property not in (select property from table2)

-- (c) Generate new dictionary items (assumes auto-incrementing ID column)
insert table2 (property)
select distinct property
from #HOLD
where property not in (select property from table2)

-- (d) Delete records containing an unknown value (assumes you didn't
--     add new dictionary items)
delete #HOLD 
where property not in (select property from table2)

##</code><code>##

-- Alter any records needing update
update table1 set
   ....
   property_id = T2.id
   ....
from table1 T1
join #HOLD H on H.PrimaryKeyColumn=T1.PrimaryKeyColumn
join table2 T2 on T2.property = H.property
where T1.property_id is null or T1.property_id != T2.id

-- Insert new records
insert table1 (..., property_id, ...)
select ..., T2.id as property_id, ...
from #HOLD H
where H.PrimaryKeyColumn not in (
   select PrimaryKeyColumn
   from table1
)