select a.claim_describe concat '; ' concat b.claim_describe
from table as a, table as b
where a.claim_number = b.claim_number

select a.claim_describe concat '; ' concat b.claim_describe concat '; ' concat c.claim_describe
from table as a, table as b, table as c
where a.claim_number = b.claim_number and a.claim_number=c.claim_number

SELECT claim_number , MIN(claim_describe) CONCAT ';' CONCAT MAX(claim_describe) 
FROM table
GROUP BY claim_number

--- your original claims table - created on-the-fly for testing
--- added claim number 2 and 3  for example purpose 
with claims (claim_number , claim_describe)  
as
(
values 
(1,  'des1.1'),
(1,  'des1.2'),
(2,'des2.1'),
(2,'des2.2'),
(2,'des2.3'),
(3,'desc3.1')
)
,
-- allocate row numbers - to obtain the sequence of concatenation 
claims_rown(rownum,claim_number,claim_describe) as 
(
select row_number() over (partition by claim_number order by claim_describe),claim_number,claim_describe from claims
)
,
-- Using recursion to concatenate claim_describe column
claims_concat(cur_rownum,cc_claim_number,concat_claim_describe) as 
(
-- 'Initialize' recursion table by fetching only the first row for each calim_number. 
select  rownum,claim_number,varchar(claim_describe,1000) from claims_rown where rownum=1 
union all   
-- Concatenate the claim_describe of current row with the previously concatenated claim_describe string 
select rownum,claim_number,concat_claim_describe||','||claim_describe from claims_rown,claims_concat where rownum=cur_rownum+1 and claim_number=cc_claim_number
)
--- Now get only the last row of the resultset for each claim_number 
select cc_claim_number as claim_number,concat_claim_describe  as claim_describe from claims_concat where (cc_claim_number,cur_rownum) in (select claim_number,max(rownum) from claims_rown group by claim_number)