How to get the discount number of customers in prior period? - sql

Question

I have a requirement where I supposed to roll customer data in the prior period of 365 days.
Table:
CREATE TABLE orders (
persistent_key_str character varying,
ord_id character varying(50),
ord_submitted_date date,
item_sku_id character varying(50),
item_extended_actual_price_amt numeric(18,2)
);
Sample data:
INSERT INTO orders VALUES
('01120736182','ORD6266073' ,'2010-12-08','100856-01',39.90),
('01120736182','ORD33997609' ,'2011-11-23','100265-01',49.99),
('01120736182','ORD33997609' ,'2011-11-23','200020-01',29.99),
('01120736182','ORD33997609' ,'2011-11-23','100817-01',44.99),
('01120736182','ORD89267964' ,'2012-12-05','200251-01',79.99),
('01120736182','ORD89267964' ,'2012-12-05','200269-01',59.99),
('01011679971','ORD89332495' ,'2012-12-05','200102-01',169.99),
('01120736182','ORD89267964' ,'2012-12-05','100907-01',89.99),
('01120736182','ORD89267964' ,'2012-12-05','200840-01',129.99),
('01120736182','ORD125155068','2013-07-27','201443-01',199.99),
('01120736182','ORD167230815','2014-06-05','200141-01',59.99),
('01011679971','ORD174927624','2014-08-16','201395-01',89.99),
('01000217334','ORD92524479' ,'2012-12-20','200021-01',29.99),
('01000217334','ORD95698491' ,'2013-01-08','200021-01',19.99),
('01000217334','ORD90683621' ,'2012-12-12','200021-01',29.990),
('01000217334','ORD92524479' ,'2012-12-20','200560-01',29.99),
('01000217334','ORD145035525','2013-12-09','200972-01',49.99),
('01000217334','ORD145035525','2013-12-09','100436-01',39.99),
('01000217334','ORD90683374' ,'2012-12-12','200284-01',39.99),
('01000217334','ORD139437285','2013-11-07','201794-01',134.99),
('01000827006','W02238550001','2010-06-11','HL 101077',349.000),
('01000827006','W01738200001','2009-12-10','EL 100310 BLK',119.96),
('01000954259','P00444170001','2009-12-03','PC 100455 BRN',389.99),
('01002319116','W02242430001','2010-06-12','TR 100966',35.99),
('01002319116','W02242430002','2010-06-12','EL 100985',99.99),
('01002319116','P00532470001','2010-05-04','HO 100482',49.99);
Using the query below I am trying to get the number of distinct customers by order_submitted_date:
select
g.order_date as "Ordered",
count(distinct o.persistent_key_str) as "customers"
from
generate_series(
(select min(ord_submitted_date) from orders),
(select max(ord_submitted_date) from orders),
'1 day'
) g (order_date)
left join
orders o on o.ord_submitted_date between g.order_date - interval '364 days'
and g.order_date
WHERE extract(year from ord_submitted_date) <= 2009
group by 1
order by 1
This is the output I expected.
Ordered Customers
2009-12-03 1
2009-12-10 1
When I execute the query above I get incorrect results.
How can I make this right?

Answer 1

To get your expected output ("the number of distinct customers") - only days with actual orders 2009:
SELECT ord_submitted_date, count(DISTINCT persistent_key_str) AS customers
FROM orders
WHERE ord_submitted_date >= '2009-1-1'
AND ord_submitted_date < '2010-1-1'
GROUP BY 1
ORDER BY 1;
Formulate the WHERE conditions this way to make the query sargable, and input easy.
If you want one row per day (from the earliest entry up to the latest in orders) - within 2009:
SELECT ord_submitted_date AS ordered
, count(DISTINCT o.persistent_key_str) AS customers
FROM (SELECT generate_series(min(ord_submitted_date) -- single query ...
, max(ord_submitted_date) -- ... to get min / max
, '1d')::date FROM orders) g (ord_submitted_date)
LEFT join orders o USING (ord_submitted_date)
WHERE ord_submitted_date >= '2009-1-1'
AND ord_submitted_date < '2010-1-1'
GROUP BY 1
ORDER BY 1;
SQL Fiddle.
Distinct customers per year
SELECT extract(year from ord_submitted_date) AS year
, count(DISTINCT persistent_key_str) AS customers
FROM orders
GROUP BY 1
ORDER BY 1;
SQL Fiddle.