Most popular pairs of shops for workers from each company - sql

Question

I've got 2 tables, one with sales and one with companies:
Sales Table
Transaction_Id Shop_id Sale_date Client_ID
92356 24234 11.09.2018 12356
92345 32121 11.09.2018 32121
94323 24321 11.09.2018 21231
94278 45321 11.09.2018 42123
Company table
Client_ID Company_name
12345 ABC
13322 ABC
32321 BCD
22221 BCD
What I want to achieve is distinct count of Clients from each Company for each pair of shops(Clients who had at least 1 transaction in both of shops) :
Shop_Id_1 Shop_id_2 Company_name Count(distinct Client_id)
12356 12345 ABC 31
12345 14278 ABC 23
14323 12345 BCD 32
14278 12345 BCD 43
I think that I have to use self join, but my queries even with filter for one week is killing DB, any thoughts on that? I'm using Microsoft SQL server 2012.
Thanks

Answer 1

I think this is a self-join and aggregation, with a twist. The twist is that you want to include the company in each sales record, so it can be used in the self-join:
with sc as (
select s.*, c.company_name
from sales s join
companies c
on s.client_id = c.client_id
)
select sc1.shop_id, sc2.shop_id, sc1.company_name, count(distinct sc1.client_id)
from sc sc1 join
sc sc2
on sc1.client_id = sc2.client_id and
sc1.company_name = sc2.company_name
group by sc1.shop_id, sc2.shop_id, sc1.company_name;

Answer 2

I think there are some issues with your question. I interpreted it as such that the company table contains the shop ID's, not the ClienId's.
First you can create a solution to get the shops as rows for each company. Here I chose a maximum of 5 shops per company. Don't forget the semicolon in the previous statement before the cte's.
WITH CTE_Comp AS
(
SELECT *, ROW_NUMBER() OVER (PARTITION BY CompanyName ORDER BY ShopID) AS RowNumb
FROM Company AS C
)
SELECT C1.ShopID,
C2.ShopID AS ShopID_2,
C3.ShopID AS ShopID_3,
C4.ShopID AS ShopID_4,
C5.ShopID AS ShopID_5,
C1.CompanyName
INTO ShopsByCompany
FROM CTE_Comp AS C1
LEFT JOIN CTE_Comp AS C2 ON C1.CompanyName= C2.CompanyName AND RowNumb = 2
LEFT JOIN CTE_Comp AS C2 ON C1.CompanyName= C3.CompanyName AND RowNumb = 3
LEFT JOIN CTE_Comp AS C2 ON C1.CompanyName= C4.CompanyName AND RowNumb = 4
LEFT JOIN CTE_Comp AS C2 ON C1.CompanyName= C5.CompanyName AND RowNumb = 5
WHERE C1.RowNumb = 1
After that, in a few steps, I think you could get the desired result:
WITH ClientsPerShop AS
(
SELECT ShopID,
COUNT (DISTINCT ClientID) AS TotalClients
FROM Sales
GROUP BY ShopID
)
, ClienstsPerCompany AS
(
SELECT CompanyName,
SUM (TotalClients) AS ClientsPerComp
FROM Company AS C
INNER JOIN ClientsPerShop AS CPS ON C.ShopID = CPS.ShopID
GROUP BY CompanyName
)
SELECT *
FROM ClienstsPerCompany AS CPA
INNER JOIN ShopsByCompany AS SBC ON SBC.CompanyName = CPA.CompanyName
Hopefully this will bring you closer to your solution, best of luck!