Merging rows to columns - sql

Question

I have the following situation (heavily abstracted, please ignore bad design):
CREATE TABLE dbo.PersonTest (Id INT, name VARCHAR(255))
INSERT INTO dbo.PersonTest
(Id, name )
VALUES (1, 'Pete')
, (1, 'Marie')
, (2, 'Sam')
, (2, 'Daisy')
I am looking for the following result:
Id Name1 Name2
1 Marie Pete
2 Daisy Sam
So, for each Id, the rows should be merged.
Getting this result I used the following query:
WITH PersonRN AS
(
SELECT *
, ROW_NUMBER() OVER(PARTITION BY Id ORDER BY name) RN
FROM dbo.PersonTest
)
SELECT PT1.Id
, PT1.name Name1
, PT2.name Name2
FROM PersonRN AS PT1
LEFT JOIN PersonRN AS PT2 -- Left join in case there's only 1 name
ON PT2.Id = PT1.Id
AND PT2.RN = 2
WHERE PT1.RN = 1
Which works perfectly fine.
My question is: Is this the best way (best in terms of performance and resilience)? If, for example, one of these Id's has a third name, this third name is ignored by my query. I'm thinking the best way to deal with that would be dynamic SQL, which would be fine, but if it can be done without dynamic, I would prefer that.

Answer 1

Aside from dynamic PIVOT, you can do this using Dynamic Crosstab, which I prefer for readability.
SQL Fiddle
DECLARE #sql1 VARCHAR(1000) = '',
#sql2 VARCHAR(1000) = '',
#sql3 VARCHAR(1000) = ''
DECLARE #max INT
SELECT TOP 1 #max = COUNT(*) FROM PersonTest GROUP BY ID ORDER BY COUNT(*) DESC
SELECT #sql1 =
'SELECT
ID' + CHAR(10)
SELECT #sql2 = #sql2 +
' , MAX(CASE WHEN RN =' + CONVERT(VARCHAR(5), RN)
+ ' THEN name END) AS ' + QUOTENAME('Name' + CONVERT(VARCHAR(5), RN)) + CHAR(10)
FROM(
SELECT TOP(#max)
ROW_NUMBER() OVER(ORDER BY (SELECT NULL)) AS RN
FROM sys.columns
)t
ORDER BY RN
SELECT #sql3 =
'FROM(
SELECT *,
RN = ROW_NUMBER() OVER(PARTITION BY ID ORDER BY name)
FROM PersonTest
)t
GROUP BY ID
ORDER BY ID'
PRINT (#sql1 + #sql2 + #sql3)
EXEC (#sql1 + #sql2 + #sql3)