Help with recursive CTE query joining to a second table - sql

Question

My objective is to recurse through table tbl and while recursing through that table select a country abbreviation (if it exists) from another table tbl2 and append those results together which are included in the final output.
The example I'll use will come from this post
tbl2 has a Foreign Key 'tbl_id' to tbl and looks like this
INSERT INTO #tbl2( Id, Abbreviation, tbl_id )
VALUES
(100, 'EU', 1)
,(101, 'AS', 2)
,(102, 'DE', 3)
,(103, 'CN', 5)
*Note: not all the countries have abbreviations.
The trick is, I want all the countries in Asia to at least show the abbreviation of Asia which is 'AS' even if a country doesn't have an abbreviation (like India for example). If the country does have an abbreviation the result needs to look like this: China:CN,AS
I've got it partly working using a subquery, but India always returns NULL for the abbreviation. It's acting like if there isn't a full recursive path back to the abbreviation, then it returns null. Maybe the solution is to use a left outer join on the abbreviation table? I've tried for hours many different variations and the subquery is as close as I can get.
WITH abcd
AS (
-- anchor
SELECT id, [Name], ParentID,
CAST(([Name]) AS VARCHAR(1000)) AS "Path"
FROM #tbl
WHERE ParentId IS NULL
UNION ALL
--recursive member
SELECT t.id, t.[Name], t.ParentID,
CAST((a.path + '/' + t.Name + ':' +
(
select t2.abbreviation + ','
from #tbl2
where t.id = t2.id
)) AS VARCHAR(1000)) AS "Path"
FROM #tbl AS t
JOIN abcd AS a
ON t.ParentId = a.id
)
SELECT * FROM abcd
btw, I'm using sql server 2005 if that matters

Answer 1

Try this example, which will give you the output (1 sample row)
id Name ParentID Path abbreviation (No column name)
5 China 2 Asia/China CN,AS Asia/China:CN,AS
The TSQL being
DECLARE #tbl TABLE (
Id INT
,[Name] VARCHAR(20)
,ParentId INT
)
INSERT INTO #tbl( Id, Name, ParentId )
VALUES
(1, 'Europe', NULL)
,(2, 'Asia', NULL)
,(3, 'Germany', 1)
,(4, 'UK', 1)
,(5, 'China', 2)
,(6, 'India', 2)
,(7, 'Scotland', 4)
,(8, 'Edinburgh', 7)
,(9, 'Leith', 8)
;
DECLARE #tbl2 table (id int, abbreviation varchar(10), tbl_id int)
INSERT INTO #tbl2( Id, Abbreviation, tbl_id )
VALUES
(100, 'EU', 1)
,(101, 'AS', 2)
,(102, 'DE', 3)
,(103, 'CN', 5)
;WITH abbr AS (
SELECT a.*, isnull(b.abbreviation,'') abbreviation
FROM #tbl a
left join #tbl2 b on a.Id = b.tbl_id
), abcd AS (
-- anchor
SELECT id, [Name], ParentID,
CAST(([Name]) AS VARCHAR(1000)) [Path],
cast(abbreviation as varchar(max)) abbreviation
FROM abbr
WHERE ParentId IS NULL
UNION ALL
--recursive member
SELECT t.id, t.[Name], t.ParentID,
CAST((a.path + '/' + t.Name) AS VARCHAR(1000)) [Path],
isnull(nullif(t.abbreviation,'')+',', '') + a.abbreviation
FROM abbr AS t
JOIN abcd AS a
ON t.ParentId = a.id
)
SELECT *, [Path] + ':' + abbreviation
FROM abcd