select username,user_id,rn from
(select rownum,count(*) as rn,username,user_id (select username , user_id from dba_users order by username)f)e
where e.rownum =1 or rownum = rn
select username,user_id,rn from
(select rownum,count(*) as rn,username,user_id (select username , user_id from dba_users order by username)f)e
where e.rownum =1 or rownum = rn
-- 这样写比较好,一次扫描。
with m as (
select username , user_id ,
count(*) over() cnt , row_number() over(order by username) rn
from dba_users
)
select * from m where rn = 1 or rn = cnt