How to get comma delimited CategoryIds recursively? - sql

Question

I have a table like this:
Name CategoryId ParentCategoryId
Footwear 93 0
Men Shoes 6 93
Female Shoes 7 93
Mobile 2 0
Smartphone 4 2
I need output like:
Name Categories
Footwear 93,0
Men Shoes 6,93,0
Female Shoes 7,93,0
Mobile 2,0
Smartphone 4,2,0
Basically, I need to recursively get the category ids and make them into a comma delimited string. I am getting into SQL after 3 years now and I have no idea how to get this result. I have tried solutions from other SO questions but still no luck.

Answer 1

You do this with recursive cte:
DECLARE #t TABLE
(
Name VARCHAR(100) ,
CategoryId INT ,
ParentCategoryId INT
)
INSERT INTO #t
VALUES ( 'Footwear', 93, 0 ),
( 'Men Shoes', 6, 93 ),
( 'Female Shoes', 7, 93 ),
( 'Mobile', 2, 0 ),
( 'Smartphone', 4, 2 );
WITH cte
AS ( SELECT * ,
CAST(CategoryId AS VARCHAR(100)) AS Categories
FROM #t
WHERE ParentCategoryId = 0
UNION ALL
SELECT t.* ,
CAST(CAST(t.CategoryId AS VARCHAR(100)) + ','
+ c.Categories AS VARCHAR(100))
FROM #t t
JOIN cte c ON c.CategoryId = t.ParentCategoryId
)
SELECT *
FROM cte

Answer 2

Try it with a recursive CTE:
DECLARE #tbl TABLE(Name VARCHAR(100),CategoryId INT,ParentCategoryId INT);
INSERT INTO #tbl VALUES
('Footwear',93,0)
,('Men Shoes',6,93)
,('Female Shoes',7,93)
,('Mobile',2,0)
,('Smartphone',4,2);
--based on this: http://stackoverflow.com/a/5522641/5089204
WITH tree (CategoryId, ParentCategoryId, level, Name, rn, IdList) as
(
SELECT CategoryId, ParentCategoryId, 0 as level, Name,
convert(varchar(max),right(row_number() over (order by CategoryId),10)) AS rn,
convert(varchar(max),ISNULL(CategoryId,0)) AS IdList
FROM #tbl
WHERE ParentCategoryId = 0
UNION ALL
SELECT c2.CategoryId, c2.ParentCategoryId, tree.level + 1, c2.Name,
rn + '/' + convert(varchar(max),right(row_number() over (order by tree.CategoryId),10)),
convert(varchar(max),c2.CategoryId) + ',' + IdList
FROM #tbl c2
INNER JOIN tree ON tree.CategoryId = c2.ParentCategoryId
)
SELECT *
FROM tree
order by RN
Part of the result:
1 Mobile 2
1/1 Smartphone 4,2
2 Footwear 93
2/1 Men Shoes 6,93
2/2 Female Shoes 7,93