How to get multiple row data in single row for one value of foreign key

Question

i want to get data from a table in a way that all the emp_id corresponding to one manager_id
in employee table come in one row. (emp_id is the primary key and manager_id is the foreign key) Since there are different emp_id whose manager_id is same
so how can i get all the emp_id in one row .

Answer 1

One way with 10g:
select mgr,
       rtrim(xmlagg(xmlelement(empno,empno||',').extract('//text()')),',')  emps
from emp
where mgr is not null
group by mgr;10g:
-- define this function:
create or replace
function concatenate(c Sys_refcursor, sep varchar2 default null) return varchar2
as
  val varchar2(100);
  return_value varchar2(4000);
begin
--  open c;
  loop
  fetch c into val;
  exit when c%notfound;
  if return_value is null then
    return_value:=val;
  else
    return_value:=return_value||sep||val;
  end if;
  end loop;
  return return_value;
end;
select mgr,
       concatenate(cursor(select empno from emp e where e.mgr=emp.mgr order by empno),',')
from emp
where mgr is not null
group by mgr;With 11g:
select mgr,
       listagg(empno,',') within group (order by empno) emps
from emp
where mgr is not null
group by mgr;