Forecasting Time series data in Oracle/SQL - sql

Question

Is there a way we can generate a time series forecasting for a data set using an Oracle analytical functions? How do we perform extrapolation in SQL/ORACLE.
Below is my need
I have data data set like below and I wanted to forecast/extrapolate for next year
Cust_id Year Revnue
1 2016 679862
1 2017 705365
1 2018 ?
2 2016 51074
2 2017 50611
2 2018 ?
3 2016 190706
3 2017 90393
3 2018 ?
4 2016 31649
4 2017 19566
4 2018 ?

Answer 1

You can create a simple forecast using the REGR linear regression functions.
--Ordinary least squares forecast for each customer for the next year.
select
cust_id,
max(year) +1 forecast_year,
-- y = mx+b
regr_slope(revenue, year)
* (max(year) + 1)
+ regr_intercept(revenue, year) forecasted_revenue
from customer_data
group by cust_id;
CUST_ID FORECAST_YEAR FORECASTED_REVENUE
------- ------------- ------------------
1 2018 730868
2 2018 50148
4 2018 7483
3 2018 -9920
Below is the sample schema. Or you can use this SQLFiddle.
create table customer_data
(
cust_id number,
year number,
revenue number
);
insert into customer_data
select 1, 2016, 679862 from dual union all
select 1, 2017, 705365 from dual union all
select 2, 2016, 51074 from dual union all
select 2, 2017, 50611 from dual union all
select 3, 2016, 190706 from dual union all
select 3, 2017, 90393 from dual union all
select 4, 2016, 31649 from dual union all
select 4, 2017, 19566 from dual;
The REGR function deals with number pairs, it doesn't understand business rules like "revenue can't be below 0". If you want to restrict the forecasts to always stay at or above 0, a CASE expression may help:
--Forecasted revenue, with minimum forecast of 0.
select cust_id, forecast_year,
case when forecasted_revenue < 0 then 0 else forecasted_revenue end forecasted_revenue
from
(
--Ordinary least squares forecast for each customer for the next year.
select
cust_id,
max(year) +1 forecast_year,
-- y = mx+b
regr_slope(revenue, year)
* (max(year) + 1)
+ regr_intercept(revenue, year) forecasted_revenue
from customer_data
group by cust_id
);
CUST_ID FORECAST_YEAR FORECASTED_REVENUE
------- ------------- ------------------
1 2018 730868
2 2018 50148
4 2018 7483
3 2018 0