Return collection from packaged function for use in select - oracle

Question

I'm currently using this block of code to return a collection of rows from my function.
--Source: http://www.adp-gmbh.ch/ora/plsql/coll/return_table.html
create or replace type t_col as object (
i number,
n varchar2(30)
);
/
create or replace type t_nested_table as table of t_col;
/
create or replace function return_table return t_nested_table as
v_ret t_nested_table;
begin
v_ret := t_nested_table();
v_ret.extend;
v_ret(v_ret.count) := t_col(1, 'one');
v_ret.extend;
v_ret(v_ret.count) := t_col(2, 'two');
v_ret.extend;
v_ret(v_ret.count) := t_col(3, 'three');
return v_ret;
end return_table;
/
Which I call by issuing SQL
select * from table(return_table);
Object types can not be defined in a package, I tried using the record type which worked (in PL/SQL) but I couldn't select from it in the same way as I can here.
How do I achieve this result using a function inside a package?

Answer 1

You could either use SQL objects inside your package or use pipelined functions (tested with 10gr2). Using SQL objects is straightforward, your actual function could be used as is inside a package.
Here's how you could use a pipelined function with a RECORD type:
SQL> CREATE OR REPLACE PACKAGE my_pkg IS
2 TYPE t_col IS RECORD(
3 i NUMBER,
4 n VARCHAR2(30));
5 TYPE t_nested_table IS TABLE OF t_col;
6 FUNCTION return_table RETURN t_nested_table PIPELINED;
7 END my_pkg;
8 /
Package created
SQL> CREATE OR REPLACE PACKAGE BODY my_pkg IS
2 FUNCTION return_table RETURN t_nested_table PIPELINED IS
3 l_row t_col;
4 BEGIN
5 l_row.i := 1;
6 l_row.n := 'one';
7 PIPE ROW(l_row);
8 l_row.i := 2;
9 l_row.n := 'two';
10 PIPE ROW(l_row);
11 RETURN;
12 END;
13 END my_pkg;
14 /
Package body created
SQL> select * from table(my_pkg.return_table);
I N
---------- ------------------------------
1 one
2 two
What happens behind the scene is that Oracle understands that since you want to use your function in a query (because of the PIPELINED keyword), you will need SQL objects, so those objects are created behind the scene for you:
SQL> select object_name
2 from user_objects o
3 where o.created > sysdate - 1
4 and object_type = 'TYPE';
OBJECT_NAME
--------------------------------------------------------------------------------
SYS_PLSQL_798806_24_1
SYS_PLSQL_798806_DUMMY_1
SYS_PLSQL_798806_9_1
SQL> select text from user_source where name='SYS_PLSQL_798806_9_1';
TEXT
--------------------------------------------------------------------------------
type SYS_PLSQL_798806_9_1 as object (I NUMBER,
N VARCHAR2(30));

Answer 2

create or replace type t_col as object (
i number,
n varchar2(30)
);
/
create or replace package foo as
type t_nested_table is table of t_col;
function return_table return t_nested_table pipelined;
end;
/
show errors
create or replace package body foo as
data t_nested_table := t_nested_table(t_col(1, 'one'),
t_col(2, 'two'),
t_col(3, 'three'));
function return_table return t_nested_table pipelined as
begin
for i in data.first .. data.last loop
pipe row(data(i));
end loop;
return;
end;
end;
/
show errors
column n format a10
select * from table(foo.return_table);
I N
---------- ----------
1 one
2 two
3 three