Pivot values on column based on grouped columns in SQL - sql

Question

I want to pivot values to columns based on a group. However, I do not know the values beforehand.
A query gives me this result.
Id Code EntityId
----------- ------------ -------------
3 22209776 1
4 143687971 3
4 143687971 4
4 143687971 5
4 143687971 15
5 143658155 7
5 143658155 8
I would like to output this
Id Code EntityId1 EntityId2 EntityId3 EntityId4
----------- ------------ ------------- ------------- ------------- -------------
3 22209776 1 NULL NULL NULL
4 143687971 3 4 5 15
5 143658155 7 8 NULL NULL

Answer 1

If you do now know how many column you are going to have in the result, you need to use dynamic T-SQL statement to build the PIVOT. For example:
IF OBJECT_ID('tempdb..#DataSource') IS NOT NULL
BEGIN;
DROP TABLE #DataSource;
END;
CREATE TABLE #DataSource
(
[id] INT
,[Code] INT
,[EntityId] INT
);
DECLARE #DynamicTSQLStatement NVARCHAR(MAX)
,#Columns NVARCHAR(MAX);
DECLARE #MaxColumns INT;
INSERT INTO #DataSource ([id], [Code], [EntityId])
VALUES (3, 22209776 , 1)
,(4, 143687971, 3)
,(4, 143687971, 4)
,(4, 143687971, 5)
,(4, 143687971, 15)
,(5, 143658155, 7)
,(5, 143658155, 8)
,(4, 143687971, 25)
,(4, 143687971, 26);
-- we need to know how many columns are going to be shown
SELECT TOP 1 #MaxColumns = COUNT(*)
FROM #DataSource
GROUP BY [Code]
ORDER BY COUNT(*) DESC;
-- we are building here the following string '[1],[2],[3],[4],[5],[6]';
-- this will change depending the input data
WITH gen AS
(
SELECT 1 AS num
UNION ALL
SELECT num+1
FROM gen
WHERE num+1<=#MaxColumns
)
SELECT #Columns = STUFF
(
(
SELECT ',[EntityId' + CAST([num] AS VARCHAR(12)) + ']'
FROM gen
FOR XML PATH(''), TYPE
).value('.', 'VARCHAR(MAX)')
,1
,1
,''
)
OPTION (maxrecursion 10000);
SET #DynamicTSQLStatement = N'
SELECT *
FROM
(
SELECT [id]
,[Code]
,[EntityId]
,''EntityId'' + CAST(ROW_NUMBER() OVER(PARTITION BY [Code] ORDER BY [EntityId]) AS VARCHAR(12))
FROM #DataSource
) DS ([id], [Code], [EntityId], [RowID])
PIVOT
(
MAX([EntityId]) for [RowID] in (' + #Columns +')
) PVT;';
EXEC sp_executesql #DynamicTSQLStatement;

Answer 2

You could try using the pivot function:
declare #tmp TABLE (id int, Code int, EntityId NVARCHAR(10))
insert into #tmp (id, Code, EntityId)
values (3, 22209776 , 1),
(4, 143687971, 3),
(4, 143687971, 4),
(4, 143687971, 5),
(4, 143687971, 15),
(5, 143658155, 7),
(5, 143658155, 8)
select
pvt.id
,pvt.Code
,[1] as EntityID1
,[2] as EntityID2
,[3] as EntityID3
,[4] as EntityID4
from (
select
id, Code, EntityId
,ROW_NUMBER() over(partition by code order by EntityId) as RowNum
from
#tmp
) a
pivot (MAX(EntityId) for RowNum in ([1], [2], [3], [4])) as pvt