示例
create table empl (
name text primary key,
boss text null
references name
on update cascade
on delete cascade
default null
);
insert into empl values ('Paul',null);
insert into empl values ('Luke','Paul');
insert into empl values ('Kate','Paul');
insert into empl values ('Marge','Kate');
insert into empl values ('Edith','Kate');
insert into empl values ('Pam','Kate');
insert into empl values ('Carol','Luke');
insert into empl values ('John','Luke');
insert into empl values ('Jack','Carol');
insert into empl values ('Alex','Carol');
with recursive t(level,path,boss,name) as (
select 0,name,boss,name from empl where boss is null
union
select
level + 1,
path || ' > ' || empl.name,
empl.boss,
empl.name
from
empl join t
onempl.boss= t.name
) select * from t order by path;
