Oracle SQL MODEL clause example: Forecasting

create table sales (
   ctry  varchar2(20),
   prod  varchar2(20),
   yr    number  ( 4),
   qty   number  ( 5)
);

insert into sales values ('Argentina', 'Table', 2020,  220);
insert into sales values ('Argentina', 'Table', 2021,  248);
insert into sales values ('Brazil',    'Table', 2020,  515);
insert into sales values ('Brazil',    'Table', 2021,  602);
insert into sales values ('Chile',     'Table', 2020,   29);
insert into sales values ('Chile',     'Table', 2021,   42);

insert into sales values ('Argentina', 'Chair', 2020,  115);
insert into sales values ('Argentina', 'Chair', 2021,  134);
insert into sales values ('Brazil',    'Chair', 2020,  297);
insert into sales values ('Brazil',    'Chair', 2021,  368);
insert into sales values ('Chile',     'Chair', 2020,   14);
insert into sales values ('Chile',     'Chair', 2021,   22);

insert into sales values ('Argentina', 'Phone', 2020, 1244);
insert into sales values ('Argentina', 'Phone', 2021, 1590);
insert into sales values ('Brazil',    'Phone', 2020, 8190);
insert into sales values ('Brazil',    'Phone', 2021,10844);
insert into sales values ('Chile',     'Phone', 2020, 3103);
insert into sales values ('Chile',     'Phone', 2021, 4965);

select 
   ctry,
   prod,
   yr,
   qty 
from 
   sales
model
   partition by (prod, ctry)
   dimension by (yr)
   measures     (qty)
   rules (
     qty[2022] = qty[2021] * (qty[2021]/qty[2020])
   )
order by
   yr,
   ctry,
   prod;