Turning sql string (with dynamic columns) into a pipelined function

Question

Hi guys,
I was working on an apex report the other day, and wrote the sql below (for those who don't know apex well, in an apex report you can define the columns at runtime.) When I was finished, I said to myself: "It would be great to have a pipeline function with this capability." So, the idea would be to have a sql string where the columns are created dynamically, depending on input parameters - and then be able to use this sql everywhere (oracle reports, sqlplus) through a pipelined function.
Here's the sql (simplified, of course, the data itself is actually not important - the LOOP is the key)
declare
v_sql varchar2(4000);
begin
v_sql := 'select client, ';
for i in (select employee from company_employees_view where condition = pi_parameter order by 1) loop
v_sql := v_sql || sum(decode(employee,''' || i.employee || ''', total)) "' || i.employee || '"';
end loop;
v_sql := v_sql || ', sum(total) "Total"';
v_sql := v_sql || ' from company_employees_view group by client';
end;
This sql would result in a final product like:
select client
, sum(decode(employee,'John',total) "John"
, sum(decode(employee,'Paul',total) "Paul"
, sum(decode(employee,'George',total) "George"
(and so on... this sql could have more or less columns depending on the input parameters of the function)
from company_employees_view
group by client;
I have tried feeding this sql into a ref cursor and an object, but always received an "inconsistent datatypes" message.
The object would be something like:
create or replace object rt_employee as (total number);
create or replace tt_employee as table of rt_employee;
create or replace object rt_client as (
client varchar2(100),
employee tt_employee);
create or replace tt_client as table of rt_client;
(I am not paying too much attention to syntax here.)
By the way, no hurry whatsoever, this is just for fun, take your time. I am using database XE with apex 2.1 and sql developer 1.2.
Thanks, Roger

Answer 1

This is the only solution I've ever seen to dynamic pipelined columns...
How to pipeline a function with a dynamic number of columns?