Recursive retrieve of child entities but with exact property match - sql

Question

I have the following tables:
Companies table:
CompanyId MotherCompanyId CompanyName
---------- ------------ ------------
1 NULL HpTopMother
2 1 HpTopDaughter1
3 2 HpTopDaughter2
4 3 HpTopDaughter3
CompanyCategories table:
CompanyCategoryId CompanyId Category
----------------- -------- -----------
1 1 Car
2 1 Lorry
3 2 Car
4 2 Lorry
5 2 Plane
6 3 Car
7 3 Lorry
8 4 Car
What I want to do is to display all the daughter companies of the head company (the Id will be passed as paramter), that have the exact match in the CompanyCategories table.
For example, in the case above only the head company, HpTopMother, and daughter company with Id 3, HpTopDaughter2, will be displayed
as both have the categories Car and Lorry.
HpTopDaughter1 will not be retrieved since it has the Plane category.
HpTopDaughter3 will not be retrieved since it does not have the Car category.
I have done the below to get all the daughters/grand-daughters of the head company:
DECLARE #companyId BIGINT
SET #companyId = 1;
WITH CTE AS
(
SELECT COM.CompanyId, COM.CompanyName
FROM Companies COM
WHERE COM.CompanyId = #companyId
UNION ALL
SELECT COM_CHILD.CompanyId, COM_CHILD.CompanyName
FROM Companies COM_CHILD JOIN cte c ON COM_CHILD.MotherCompanyId = c.CompanyId
INNER JOIN CompanyCategories CC ON CC.CompanyId = c.CompanyId
INNER JOIN CompanyCategories CC_CHILD on CC_CHILD.CompanyId = COR_CHILD.CompanyId and CC.Category = CC_CHILD.Category
)
SELECT CompanyId, CompanyName
FROM CTE
However, this is returning all the companies. Any idea of how I can achieve the listing of all the daughters/grand-daughters companies but only those having an exact category match?

Answer 1

Check if category sets are the same for the top level company and its descendants
DECLARE #companyId BIGINT
SET #companyId = 1;
WITH rcats as(
select null a, 1 b, category
from CompanyCategories CC
where CC.companyId = #companyId
), CTE AS
(
SELECT COM.CompanyId, COM.CompanyName
FROM Companies COM
WHERE COM.CompanyId = #companyId
UNION ALL
SELECT COM_CHILD.CompanyId, COM_CHILD.CompanyName
FROM Companies COM_CHILD
JOIN cte c ON COM_CHILD.MotherCompanyId = c.CompanyId
)
SELECT CompanyId, CompanyName
FROM CTE c
where not exists (
select 1
from
( select 1 a, null b, category
from CompanyCategories CC
where CC.CompanyId = c.CompanyId
union all
select a, b, category
from rcats
) t
group by category
having count(a) <> count(b)
)
db<>fiddle

Answer 2

Use CTE to search for parent-child chains and then filter out companies according to your condition using Not Exist and Except.
Declare #ID Int = 1;
With A As
( Select CompanyId, CompanyName, Row_Number() Over (Order by CompanyId) As Num
From Companies
Where CompanyId = #ID
Union All
Select Companies.CompanyId, Companies.CompanyName, A.Num
From Companies Inner Join A On (Companies.MotherCompanyId=A.CompanyId)
)
Select A.Num, A.CompanyName, String_Agg(C.Category,',') As Categories
From A Inner Join A As A_1 On (A.Num=A_1.Num)
Inner Join CompanyCategories As C On (A.CompanyId=C.CompanyId)
Where A.CompanyId<>A_1.CompanyId And
Not Exists (Select Category From CompanyCategories
Where A_1.CompanyId=CompanyCategories.CompanyId
Except
Select Category From CompanyCategories
Where A.CompanyId=CompanyCategories.CompanyId) And
Not Exists (Select Category From CompanyCategories
Where A.CompanyId=CompanyCategories.CompanyId
Except
Select Category From CompanyCategories
Where A_1.CompanyId=CompanyCategories.CompanyId)
Group by A.Num, A.CompanyName
Order by A.Num, A.CompanyName Desc
db<>fiddle
Result
Num
CompanyName
Categories
1
HpTopMother
Car,Lorry
1
HpTopDaughter2
Car,Lorry
to get companies with the same categories as the company associated with #ID, use the following query:
Declare #ID Int = 1;
With A As
( Select CompanyId, CompanyName, Row_Number() Over (Order by CompanyId) As Num
From Companies
Where CompanyId = #ID
Union All
Select Companies.CompanyId, Companies.CompanyName, A.Num
From Companies Inner Join A On (Companies.MotherCompanyId=A.CompanyId)
)
Select A.Num, A.CompanyName, String_Agg(C.Category,',') As Categories
From A Inner Join A As A_1 On (A.Num=A_1.Num)
Inner Join CompanyCategories As C On (A_1.CompanyId=C.CompanyId)
Where A_1.CompanyId = #ID
And Not Exists (Select Category From CompanyCategories
Where A_1.CompanyId=CompanyCategories.CompanyId
Except
Select Category From CompanyCategories
Where A.CompanyId=CompanyCategories.CompanyId)
And Not Exists (Select Category From CompanyCategories
Where A.CompanyId=CompanyCategories.CompanyId
Except
Select Category From CompanyCategories
Where A_1.CompanyId=CompanyCategories.CompanyId)
Group by A.Num, A.CompanyName
Order by A.Num, A.CompanyName Desc