Mutually exclusive counts in SQL - sql

Question

The table that I need to query looks like this
ID - Account - Product
1 - 002 - Bike
2 - 003 - Bike
4 - 003 - Motor
5 - 004 - Car
I need to be able to retrieve the number of accounts that purchased the each of the products and combinations of the products, like this
Bike | Car | Motor | Bike&Car | Bike&Motor | Car&Motor | Bike&Car&Motor
Note that an account that purchased a combination of products will be counted as 1.
Please help me in retrieving this data.

Answer 1

You can do this using two levels of aggregation. One method puts the values on different rows:
select has_bike, has_motor, has_car, count(*)
from (select account,
max(case when product = 'bike' then 1 else 0 end) as has_bike,
max(case when product = 'motor' then 1 else 0 end) as has_motor,
max(case when product = 'car' then 1 else 0 end) as has_car
from t
group by account
) t
group by has_bike, has_motor, has_car;
Or in columns:
select sum(has_bike * (1 - has_motor) * (1 - has_car)) as has_only_bike,
sum((1 - has_bike) * has_motor * (1 - has_car)) as has_only_motor,
sum((1 - has_bike) * (1 - has_motor) * has_car) as has_only_car,
. . .
from (select account,
max(case when product = 'bike' then 1 else 0 end) as has_bike,
max(case when product = 'motor' then 1 else 0 end) as has_motor,
max(case when product = 'car' then 1 else 0 end) as has_car
from t
group by account
) t;

Answer 2

If you only have a limited set of Products, then you can use this:
-- Create sample data
CREATE TABLE #tbl(
ID INT,
Account VARCHAR(10),
Product VARCHAR(10)
);
INSERT INTO #tbl VALUES
(1, '002', 'Bike'),
(2, '003', 'Bike'),
(3, '003', 'Motor'),
(4, '004', 'Car');
WITH Cte AS(
SELECT t1.Account, a.Products
FROM #tbl t1
CROSS APPLY (
SELECT STUFF((
SELECT '&' + t2.Product
FROM #tbl t2
WHERE t2.Account = t1.Account
ORDER BY t2.Product
FOR XML PATH(''), type).value('.[1]','nvarchar(max)'),
1, 1, '') AS Products
) a
GROUP BY t1.Account, a.Products
)
SELECT
Bike = SUM(CASE WHEN Products = 'Bike' THEN 1 ELSE 0 END),
Car = SUM(CASE WHEN Products = 'Car' THEN 1 ELSE 0 END),
Motor = SUM(CASE WHEN Products = 'Motor' THEN 1 ELSE 0 END),
[Bike&Car] = SUM(CASE WHEN Products = 'Bike&Car' THEN 1 ELSE 0 END),
[Bike&Motor] = SUM(CASE WHEN Products = 'Bike&Motor' THEN 1 ELSE 0 END),
[Car&Motor] = SUM(CASE WHEN Products = 'Car&Motor' THEN 1 ELSE 0 END),
[Bike&Car&Motor] = SUM(CASE WHEN Products = 'Bike&Car&Motor' THEN 1 ELSE 0 END)
FROM Cte;
DROP TABLE #tbl; -- Remove sample data
The idea is to generate 1 row for each Account, together with a comma-delimited Products. If you execute the query inside the CTE, you will get:
Account Products
---------- ---------------
002 Bike
003 Bike&Motor
004 Car
With that, you can do a conditional aggregation. The above uses a static solution, if you do not know the number of Products, you may need to come up with a dynamic approach.
ONLINE DEMO