Dynamic column creation with Oracle SQL - sql

Question

Currently I am working on fixed asset register report wand and I need to add Projection columns in main query.
Depreciation Remaining Life of
Assed_No Amount asset in months
-------- ------------ -----------------
1 400 6
2 200 3
3 100 4
4 600 1
Now, I want modification in SQL that according remaining life of asset in months column should generate. For 1st asset remaining life of asset in months is 6, so total 6 projection columns should come with value as 400. If remaining life is less than maximum no. i.e 6 then it should give 0 for rest of columns.
I want final solution like below,
Depreciation Remaining Life of
Assed_No Amount asset in months Projection 1 Projection 2 Projection 3 Projection 4 Projection 5 Projection 6
-------- ------------ ----------------- ------------ ------------ ------------ ------------ ------------ ------------
1 400 6 400 400 400 400 400 400
2 200 3 200 200 0 0 0 0
3 100 4 100 100 100 100 0 0
4 600 1 600 0 0 0 0 0

Answer 1

You can use a simple case expression for each projection:
-- CTE for sample data
with your_table (asset_no, amount, remaining_months) as (
select 1, 400, 6 from dual
union all select 2, 200, 3 from dual
union all select 3, 100, 4 from dual
union all select 4, 600, 1 from dual
)
-- query using my CTE column names
select asset_no, amount, remaining_months,
case when remaining_months >= 1 then amount else 0 end as proj_1,
case when remaining_months >= 2 then amount else 0 end as proj_2,
case when remaining_months >= 3 then amount else 0 end as proj_3,
case when remaining_months >= 4 then amount else 0 end as proj_4,
case when remaining_months >= 5 then amount else 0 end as proj_5,
case when remaining_months >= 6 then amount else 0 end as proj_6
from your_table;
ASSET_NO AMOUNT REMAINING_MONTHS PROJ_1 PROJ_2 PROJ_3 PROJ_4 PROJ_5 PROJ_6
---------- ---------- ---------------- ---------- ---------- ---------- ---------- ---------- ----------
1 400 6 400 400 400 400 400 400
2 200 3 200 200 200 0 0 0
3 100 4 100 100 100 100 0 0
4 600 1 600 0 0 0 0 0

Answer 2

This is basically the dynamic version of Alex's query ( as a bonus !)
Note the use of refcursor Bind variables. This will work when you run it in SQl* Plus or as script (F5) in SQL developer or Toad.
You may also use DBMS_SQL.RETURN_RESULT in Oracle 12c and above to do the same.
VARIABLE x REFCURSOR;
DECLARE
v_case_expr VARCHAR2(1000);
BEGIN
SELECT
listagg('CASE WHEN remaining_months > = '
|| level
|| '
then amount else 0 end as proj_'
|| level,',') WITHIN GROUP ( ORDER BY level)
INTO v_case_expr
FROM
dual
CONNECT BY
level <= (
SELECT
MAX(remaining_months)
FROM
assets
);
OPEN :x FOR 'select asset_no, amount, remaining_months, '
|| v_case_expr
|| ' FROM assets';END;
/
PRINT x;
PL/SQL procedure successfully completed.
ASSET_NO AMOUNT REMAINING_MONTHS PROJ_1 PROJ_2 PROJ_3 PROJ_4 PROJ_5 PROJ_6
---------- ---------- ---------------- ---------- ---------- ---------- ---------- ---------- ----------
1 400 6 400 400 400 400 400 400
2 200 3 200 200 200 0 0 0
3 100 4 100 100 100 100 0 0
4 600 1 600 0 0 0 0 0

Answer 3

When the amount of calculations increase sometimes pivot could be better.
Here I use a cartesian product before, to create the data:
with dat (asset_no, dep_amount, r_life)as
( select 1, 400, 6 from dual union all
select 2, 200, 3 from dual union all
select 3, 100, 4 from dual union all
select 4, 600, 1 from dual )
, mon as (select level lv from dual connect by level <= 6)
, bas as (
select asset_no, dep_amount, r_life, lv, case when r_life >= lv then dep_amount else 0 end proj_m from dat, mon)
select *
from bas
pivot(sum(proj_m) for lv in (1 as proj_1,2 as proj_2,3 as proj_3,4 as proj_4,5 as proj_5,6 as proj_6))
order by asset_no
Think the solution with case expressions is better here