Pivot duplicate column names and get all values for columns - sql

Question

EXPLAINATION
Imagine that I have 2 tables. FormFields where are stored column names as values, which should be pivoted and second table FilledValues with user's filled values with FormFieldId provided.
PROBLEM
As you see (below in SAMPLE section) in FormFields table I have duplicate names, but different ID's. I need to make that after joining tables, all values from FilledValues table will be assiged to column names, not to Id's.
What I need better you will see in OUTPUT section below.
SAMPLE DATA
FormFields
ID Name GroupId
1 col1 1
2 col2 1
3 col3 1
4 col1 2
5 col2 2
6 col3 2
FilledValues
ID Name FormFieldId GroupID
1 a 2 1
2 b 3 1
3 c 1 1
4 d 4 2
5 e 6 2
6 f 5 2
OUTPUT FOR NOW
col1 col2 col3
c a b -- As you see It returning only values for FormFieldId 1 2 3
-- d, e, f are lost that because It have duplicate col names, but different id's
DESIRED OUTPUT
col1 col2 col3
c a b
e f d
QUERY
SELECT * FROM
(
SELECT FF.Name AS NamePiv,
FV.Name AS Val1
FROM FormFields FF
JOIN FilledValues FV ON FF.Id = FV.FormFieldId
) x
PIVOT
(
MIN(Val1)
FOR NamePiv IN ([col1],[col2],[col3])
) piv
SQL FIDDLE
How can I produce the OUTPUT with the multiple rows?

Answer 1

Since you are using PIVOT the data is being aggregated so you only return one value for each column being grouped. You don't have any columns in your subquery that are unique and being used in the grouping aspect of PIVOT to return multiple rows. In order to do this you need some value. If you have a column with a unique value for each "group" then you would use that or you can use a windowing function like row_number().
row_number() will create a sequenced number for each FF.Name meaning if you have 2 col1 you will generate a 1 for a row and a 2 for another row. Once this is included in your subquery, you now have a unique value that is used when aggregating your data and you will return multiple rows:
SELECT [col1],[col2],[col3]
FROM
(
SELECT
FF.Name AS NamePiv,
FV.Name AS Val1,
rn = row_number() over(partition by ff.Name order by fv.Id)
FROM FormFields FF
JOIN FilledValues FV ON FF.Id = FV.FormFieldId
) x
PIVOT
(
MIN(Val1)
FOR NamePiv IN ([col1],[col2],[col3])
) piv;
See SQL Fiddle with Demo. The output is:
| col1 | col2 | col3 |
|------|------|------|
| c | a | b |
| e | f | d |

Answer 2

Just adding GroupId in Pivot source query will fix your problem
SELECT * FROM (
SELECT FF.Name AS NamePiv,
FV.Name AS Val1,
ff.groupid
FROM FormFields FF
JOIN FilledValues FV ON FF.Id = FV.FormFieldId
) x
PIVOT
(
MIN(Val1)
FOR NamePiv IN ([col1],[col2],[col3])
) piv
SQLFIDDLE DEMO

Answer 3

I would be inclined to do this with conditional aggregation:
select max(case when formfieldid % 3 = 1 then name end) as col1,
max(case when formfieldid % 3 = 2 then name end) as col2,
max(case when formfieldid % 3 = 0 then name end) as col3
from FilledValues
group by GroupID;
It is unclear what the rule is for assigning a value to a column. This uses the remainder, which works for your input data.