T-SQL Left-Join with 1 row (limi, subselect) - sql

Question

I already read a lot on that topic but I´m unable to get it to work for my case.
I have the following situation:
A list of orderitems (the main datasets I want to get)
Articles which have a 1:1 relation to an order item
A n:m Jointable "Articlesupplier" which creates a relation between an article and a
partner
A Partner table with detailed information about partners.
Target:
One dataset per OrderItem and from the suppliers I only want to get the first one found in the join. No priorization required.
Tables:
Table IDX_ORDERITEM
id,article_id
Table IDX_ARTICLE
id,name
Table IDX_ARTICLESUPPLIER
article_id,partner_id
Table IDX_PARTNER
id,abbr
My actual statement (short version):
SELECT IDX_ORDERITEM.id
FROM
dbo.IDX_ORDERITEM AS IDX_ORDERITEM
-- ARTICLE --
INNER JOIN dbo.IDX_ARTICLE AS IDX_ARTICLE
ON IDX_ORDERITEM.article_id=IDX_ARTICLE.id
-- SUPPLIER VIA ARTICLE --
LEFT JOIN
(SELECT TOP(1) IDX_PARTNER.id, IDX_PARTNER.abbr
FROM IDX_PARTNER, IDX_ARTICLESUPPLIER
WHERE IDX_PARTNER.id = IDX_ARTICLESUPPLIER.partner_id
AND IDX_ARTICLESUPPLIER.article_id=IDX_ARTICLE.id) AS IDX_PARTNER_SUPPLIER
ON IDX_PARTNER_SUPPLIER.id=IDX_ARTICLE.supplier_partner_id
WHERE 1>0
ORDER BY orderitem.id DESC
But it seems I can´t access IDX_ARTICLE.id in the subquery. I get the following error message:
The multi-part identifier "IDX_ARTICLE.id" could not be bound.
Is the problem that the Article alias has the same name as the table name?
Thanks a lot in advance for possible ideas,
Mike

Answer 1

Well, I changed your aliases, and the subquery to which you were joining (I also modified that subquery so it doesn't use implicit joins anymore), though this changes where mostly cosmetics. The actual important change was the use of OUTER APPLY instead of LEFT JOIN:
SELECT OI.id
FROM dbo.IDX_ORDERITEM AS OI
INNER JOIN dbo.IDX_ARTICLE AS A
ON OI.article_id = A.id
OUTER APPLY
(SELECT TOP(1) P.id, P.abbr
FROM IDX_PARTNER AS P
INNER JOIN IDX_ARTICLESUPPLIER AS SUP
ON P.id = SUP.partner_id
WHERE SUP.article_id = A.id
AND P.id = A.supplier_partner_id) AS PS
ORDER BY OI.id DESC

Answer 2

The error is thrown because the below piece of query
(SELECT TOP(1) IDX_PARTNER.id, IDX_PARTNER.abbr
FROM IDX_PARTNER, IDX_ARTICLESUPPLIER
WHERE IDX_PARTNER.id = IDX_ARTICLESUPPLIER.partner_id
AND IDX_ARTICLESUPPLIER.article_id=IDX_ARTICLE.id) AS IDX_PARTNER_SUPPLIER
cannot be considered as a correlated sub-query and IDX_ARTICLE.id is referenced in it in the same manner we reference a field of outer query in a correlated sub-query.

Answer 3

I see two problems.
According to your DDLs there is no IDX_ARTICLE.supplier_partner_id which you refer to in the left join on clause.
Second, I'm quite sure you cannot use IDX_ARTICLE.id in your derived table. Simply add IDX_ARTICLESUPPLIER.article_id to your derived table selected fields and use it in your left join on clause against IDX_ARTICLE.id.

Answer 4

I prefer to avoid nested queries. If I can, I will always rewrite it using CTE.
WITH Part_Sup
AS (
SELECT TOP ( 1 ) P.id
,P.abbr
,SUP.article_id
FROM IDX_PARTNER AS P
INNER JOIN IDX_ARTICLESUPPLIER AS SUP
ON P.id = SUP.partner_id
)
SELECT OI.id
FROM dbo.IDX_ORDERITEM AS OI
INNER JOIN dbo.IDX_ARTICLE AS A
ON OI.article_id = A.id
LEFT OUTER JOIN Part_Sup AS PS
ON PS.article_id = A.Id
AND PS.id = A.supplier_partner_id
ORDER BY OI.id DESC;
Next I rewritten the first query to use ROW_NUMBER() function instead of using TOP (1) using ROW_NUMBER you can control which results you want and what you don't want.
WITH Part_Sup
AS (
SELECT P.id
,P.abbr
,SUP.article_id
,ROW_NUMBER() OVER ( PARTITION BY P.id, P.abbr ) AS RowNum
FROM IDX_PARTNER AS P
INNER JOIN IDX_ARTICLESUPPLIER AS SUP
ON P.id = SUP.partner_id
)
SELECT OI.id
FROM dbo.IDX_ORDERITEM AS OI
INNER JOIN dbo.IDX_ARTICLE AS A
ON OI.article_id = A.id
LEFT OUTER JOIN Part_Sup AS PS
ON PS.article_id = A.Id
AND PS.id = A.supplier_partner_id
AND RowNum = 1
ORDER BY OI.id DESC;

Answer 5

Thanks Lamak - you solved it :)
I used your input to extract the basic solution to make it a bit easier to read for others which have the same problem:
Using OUTER APPLY (without ORDER_ITEM Table here):
SELECT IDX_ARTICLE.id AS AR_ID, IDX_PARTNER_SUPPLIER.id, IDX_PARTNER_SUPPLIER.abbr
FROM
dbo.IDX_ARTICLE AS IDX_ARTICLE
OUTER APPLY
(SELECT TOP(1) _PARTNER.id, _PARTNER.abbr
FROM IDX_PARTNER AS _PARTNER
INNER JOIN IDX_ARTICLESUPPLIER AS _ARTICLESUPPLIER
ON _PARTNER.id = _ARTICLESUPPLIER.partner_id
WHERE _ARTICLESUPPLIER.article_id=IDX_ARTICLE.id
AND _ARTICLESUPPLIER.deleted IS NULL) AS IDX_PARTNER_SUPPLIER
WHERE IDX_ARTICLE.id=67