用SQL得到全排列

create table Elements
(
    i int not null primary key
)
GO
insert into Elements
values (1),(2),(3),(4),(5),(6),(7);

With ElementsWithWeight as
(
    select
        i,
        power(2,(i-1)) as wgt
    from
        Elements
)
select
    E1.i, E2.i, E3.i, E4.i, E5.i, E6.i, E7.i
from
    ElementsWithWeight as E1,
    ElementsWithWeight as E2,
    ElementsWithWeight as E3,
    ElementsWithWeight as E4,
    ElementsWithWeight as E5,
    ElementsWithWeight as E6,
    ElementsWithWeight as E7
where
    (E1.wgt + E2.wgt + E3.wgt + E4.wgt + E5.wgt + E6.wgt + E7.wgt) = 127

create table users (name char(2),value char(1),id number);
insert into users values('甲','a',1);
insert into users values('乙','b',2);
insert into users values('丙','c',3);
insert into users values('丁','d',4);
commit;

select o.p as "排列" from
  (select replace (sys_connect_by_path( value, ',' ) , ',' ) p
  from users connect by nocycle value != prior value) o
  where length(o.p) =2;

select o.p as "排列" from
   (select replace (sys_connect_by_path( value, ',' ) , ',' ) p
   from users connect by nocycle value != prior value) o
   where length(o.p) =3;

select o.p as "排列" from
   (select replace (sys_connect_by_path( value, ',' ) , ',' ) p
   from users connect by nocycle value != prior value) o
   where length(o.p) =4;