Using ROW_NUMBER instead of MAX() - sql-server

Question

My question is related to this one. I have the following query to get the mother tongue and the fluent languages for an employee :
SELECT
lan.AdminFileId
,MAX(lan.MotherTongue) AS MotherTongue
,MAX(lan.Fluent) AS Fluent
FROM (SELECT
al.AdminFileId
,MAX(CASE
WHEN al.LanguageLevelId = 4 THEN l.Label
END) AS MotherTongue
,MAX(CASE
WHEN al.LanguageLevelId = 2 THEN l.Label
END) AS Fluent
FROM AF_Language al
LEFT JOIN AF_AdminFile aaf ON aaf.AdminFileId=al.AdminFileId
INNER JOIN Employee e ON e.AdminFileId=aaf.AdminFileId
LEFT JOIN Language l ON al.LanguageId = l.ID
GROUP BY al.AdminFileId
,l.Label
,al.LanguageLevelId) AS lan
GROUP BY lan.AdminFileId
The output is like below :
AdminFileId MotherTongue Fluent
45 English French
67 Spanish English
88 Arabic English
How can I use ROW_NUMBER to get the same result?
Essentially

Answer 1

I think you don't need to use ROW_NUMBER(), use AdminFileId only in GROUP BY clause will have only single entry :
SELECT al.AdminFileId,
MAX(CASE WHEN al.LanguageLevelId = 4 THEN l.Label END) AS MotherTongue,
MAX(CASE WHEN al.LanguageLevelId = 2 THEN l.Label END) AS Fluent
FROM AF_Language al LEFT JOIN
AF_AdminFile aaf
ON aaf.AdminFileId = al.AdminFileId LEFT JOIN -- Used LEFT JOIN INSTEAD OF INNER
Employee e
ON e.AdminFileId = aaf.AdminFileId LEFT JOIN
Language l
ON al.LanguageId = l.ID
GROUP BY al.AdminFileId;
EDIT : Using row_number :
SELECT al.AdminFileId, l.Label,
ROW_NUMBER() OVER (PARTITION BY al.AdminFileId
ORDER BY (CASE WHEN al.LanguageLevelId = 4
THEN 1 ELSE 2
END)
) AS Seq
FROM AF_Language al LEFT JOIN
AF_AdminFile aaf
ON aaf.AdminFileId = al.AdminFileId LEFT JOIN -- Used LEFT JOIN INSTEAD OF INNER
Employee e
ON e.AdminFileId = aaf.AdminFileId LEFT JOIN
Language l
ON al.LanguageId = l.ID
WHERE al.LanguageLevelId IN (4, 2);
Then you can use sub-query :
SELECT AdminFileId,
MAX(CASE WHEN Seq = 1 THEN Label END) AS MotherTongue,
MAX(CASE WHEN Seq = 2 THEN Label END) AS Fluent
FROM ( <Query>
) t
GROUP BY AdminFileId;