wc_id (primary key)
wc_no
wc_dt
deal_cd

wc_id  foreign key
CLAIM_CDDET

select a.wc_id
from warr_abroad b,sv_warr a
where b.CLAIM_CDDET=nvl(:status,b.CLAIM_CDDET)
and a.wc_id=b.wc_id

select a.wc_id
from warr_abroad b,sv_warr a
where a.wc_id=b.wc_id
  &lex_status

if :status is null then
   :lex_status := 'and 1 = 1';     -- fetch all records
else
   :lex_status := 'and b.claim_cddet = :status';
   -- or, possibly, 'and b.claim_cddet = ' || :status;
end if;

where ((:status is null and 1=1) or
       (:status is not null and b.CLAIM_CDDET=:status))

   :lex_status := 'and 1 = 1';     -- fetch all records

   :lex_status := 'and b.claim_cddet = :status';