Oracle Query: Loop through columns dynamically to create rows - oracle

Question

I have the following Oracle database that can have any number of columns that may grow over time by user intervention in the web application.
ID | Name | Football | WhoCreated | When | Baseball | Cheerleading | Swimming
1 | Billy | (null) | sam, smith | (Timestamp)| 1 | (null) | 1
2 | Susie | 1 | sam, smith | (Timestamp)| (null) | 1 | 1
3 | Johnny | 1 | Homer | (Timestamp)| 1 | (null) | (null)
I am trying to generate an output that looks like
2, Susie, Football
3, Johnny, Football
1, Billy, Baseball
3, Johnny, Baseball
2, Susie, Cheerleading
1, Billy, Swimming
2, Susie, Swimming
I can do this with a UNION, but I will have to adjust each for the specific name field. I'm already up to about 50 columns (50 unions), and that can grow at any time by users in the system. To further complicate things, I have a few columns for auditing purposes tucked in the middle of the list. I really need some sort of dynamic way of looping through the columns, I have searched, but none seem to address the issue I have.

Answer 1

This should give you an idea. I couldn't test it, but fairly simple to understand.
create or replace package test_pkg AS
TYPE REP_CURS IS REF CURSOR;
TYPE output_REC IS RECORD(
id_ number,
name_ varchar2(50),
field_ varchar2(50));
TYPE output_TAB IS TABLE OF output_REC;
FUNCTION Get_Data RETURN output_TAB
PIPELINED;
END test_pkg;
CREATE OR REPLACE PACKAGE BODY test_pkg IS
FUNCTION Get_Data RETURN output_TAB
PIPELINED IS
output_REC_ output_REC;
rep_lines_ REP_CURS;
stmt_ VARCHAR2(5000);
table_rec_ yourtable%ROWTYPE;
begin
stmt_ := ' YOUR QUERY HERE ';
OPEN rep_lines_ FOR stmt_;
LOOP
FETCH rep_lines_
INTO table_rec_;
EXIT WHEN rep_lines_%NOTFOUND;
output_REC_.id_ := table_rec_.id;
output_REC_.name_ := table_rec_.name;
if table_rec_.football IS not null then
output_REC_.field_ := table_rec_.football;
PIPE ROW(output_REC_);
end if;
if table_rec_.Baseball IS not null then
output_REC_.field_ := table_rec_.Baseball;
PIPE ROW(output_REC_);
end if;
if table_rec_.Cheerleading IS not null then
output_REC_.field_ := table_rec_.Cheerleading;
PIPE ROW(output_REC_);
end if;
if table_rec_.Swimming IS not null then
output_REC_.field_ := table_rec_.Swimming;
PIPE ROW(output_REC_);
end if;
END LOOP;
CLOSE rep_lines_;
RETURN;
exception
when others then
DBMS_OUTPUT.put_line('Error:' || DBMS_UTILITY.FORMAT_ERROR_BACKTRACE ||
DBMS_UTILITY.FORMAT_ERROR_STACK ||
DBMS_UTILITY.FORMAT_CALL_STACK);
END Get_Data;
END test_pkg;

Answer 2

You should create a function and then use it, please consider the code below:
CREATE OR REPLACE FUNCTION commalist (par_id NUMBER) RETURN VARCHAR2 IS
TYPE curs IS REF CURSOR;
v_emp_cursor curs;
fieldvalue VARCHAR2(4000);
var_out VARCHAR2(4000);
CURSOR col IS
SELECT column_name
FROM user_tab_columns
WHERE table_name = 'TABLE';
BEGIN
FOR reccol IN col LOOP
OPEN v_emp_cursor FOR ('SELECT '||reccol.column_name||' val
FROM TABLE
WHERE id = '||par_id);
LOOP
FETCH v_emp_cursor INTO fieldvalue;
IF fieldvalue IS NOT NULL THEN
var_out := var_out||fieldvalue||', ';
END IF;
EXIT WHEN v_emp_cursor%NOTFOUND;
END LOOP;
CLOSE v_emp_cursor;
END LOOP;
RETURN SubStr(var_out, 0, Length(var_out) - 2);
END;

Answer 3

Try this
with src as (select 1 ID, 'Billy' name, 0 Football, 'sam smith' WhoCreated, sysTimestamp when,
1 Baseball, cast(null as number) Cheerleading, 1 Swimming
from dual
union all
select 2, 'Susie', 1, 'sam smith', sysTimestamp, null, 1, 1
from dual
union all
select 3, 'Johnny', 1, 'Homer', sysTimestamp, 1, null, null
from dual),
unpivottbl as (select *
from src
UNPIVOT
(
VAL
FOR descript
IN (Football, Baseball, Cheerleading, Swimming)
))
select ID, name, descript
from unpivottbl
where VAL = 1
Though it is not dynamic solution, you will need to add the columns for which you are going to unpivot the data. This is reference for unpivot.