SQL retrieving tree structure query - sql

Question

I have 2 tables
Products table:
ID ProductName Category
0 T-Shirt 15
1 Aqua De Gio 12
2 Jacket 15
3 Hot Water 13
Categories table:
categoryID catagoryName highercategoryID
8 Fragnance 0
99 Clothing 0
15 Armani Clothing 99
12 Armani Fragnance 8
102 Davidoff Fragnance 8
Expected result
ID ProductName Category CategoryTree
0 T-Shirt 15 Clothing > Armani Cloting
1 Aqua De Gio 12 Fragnance > Armani Fragnance
2 Jacket 15 Clothing > Armani Cloting
3 Hot Water 13 Fragnance > Davidoff Fragnance
For example take the T-Shirt from the products table
its category is 15.
go for the categories table and see where categoryID=15
look at the highercategoryID if its = 0 stop, if not then take its value 99
look for 99 in the categoryID column, the higher category now is 0 so stop.
based on the above I need to get "Clothing > Armani Clothing".
I am new to SQL queries and here is my first try
select
x.*,
x.p1 + isnull((' > ' + x.c1), '') + isnull((' > ' + x.c2), '') as CategoryTree
from
(select
RP.categoryid as catid,
RP.catagoryName as p1,
R1.catagoryName as c1,
R2.catagoryName as c2
from
categories as RP
left outer join
categories as R1 on R1.highercategoryid = RP.categoryid
left outer join
categories as R2 on R2.highercategoryid = R1.categoryid
left outer join
categories as R3 on R3.highercategoryid = R2.categoryid
where
RP.highercategoryid != 0 ) x
I am not sure how to stop the joining when I find the 0 value in the higher category, and how to join the products on their categories, and is there a dynamic way without using a lot of joins?

Answer 1

Here it goes:
With CTE (CatID, CatName, HigherCatID) AS
(
SELECT categoryID, CAST(catagoryName AS VARCHAR(1000)), highercategoryID
FROM CATEGORIES
UNION ALL
SELECT C.categoryID, CAST(CTE.CatName + ' > ' + C.catagoryName AS VARCHAR(1000)), CTE.HigherCatID
FROM CATEGORIES C
INNER JOIN CTE ON C.HigherCategoryID = CTE.CatID
)
SELECT P.ID, P.ProductName, Cte.CatID, CTE.CatName
FROM CTE INNER JOIN PRODUCTS P
ON (CatID = P.Category)
WHERE CTE.HigherCatID=0
you got a SQLFiddle Here