How to transform rows into column? [duplicate] - sql

Question

This question already has answers here:
Convert Rows to columns using 'Pivot' in SQL Server
(9 answers)
Closed 7 years ago.
I have a table like this and there are only two feature for all user in this table
+-------+---------+-----------+----------+
| User | Feature | StartDate | EndDate |
+-------+---------+-----------+----------+
| Peter | F1 | 2015/1/1 | 2015/2/1 |
| Peter | F2 | 2015/3/1 | 2015/4/1 |
| John | F1 | 2015/5/1 | 2015/6/1 |
| John | F2 | 2015/7/1 | 2015/8/1 |
+-------+---------+-----------+----------+
I want to transform to
+-------+--------------+------------+--------------+------------+
| User | F1_StartDate | F1_EndDate | F2_StartDate | F2_EndDate |
+-------+--------------+------------+--------------+------------+
| Peter | 2015/1/1 | 2015/2/1 | 2015/3/1 | 2015/4/1 |
| John | 2015/5/1 | 2015/6/1 | 2015/7/1 | 2015/8/1 |
+-------+--------------+------------+--------------+------------+

Answer 1

If you are using SQL Server 2005 or up by any chance, PIVOT is what you are looking for.

Answer 2

The best general way to perform this sort of operation is a simple group by statement. This should work across all major ODBMS:
select user,
max(case when feature='F1' then StartDate else null end) F1_StartDate,
max(case when feature='F1' then EndDate else null end) F1_EndDate,
max(case when feature='F2' then StartDate else null end) F2_StartDate,
max(case when feature='F2' then EndDate else null end) F2_EndDate
from table
group by user
Note: as mentioned in the comments, this is often bad practice, as depending on your needs, it can make the data harder to work with. However, there are cases where it makes sense, when you have a small, limited number of values.

Answer 3

This is a bit of a hack with a CTE:
;WITH CTE AS (
SELECT [User], [Feature] + '_StartDate' AS [Type], StartDate AS [Date]
FROM Table1
UNION ALL
SELECT [User], [Feature] + '_EndDate' AS [Type], EndDate AS [Date]
FROM Table1)
SELECT * FROM CTE
PIVOT(MAX([Date]) FOR [Type] IN ([F1_StartDate],[F2_StartDate], [F1_EndDate], [F2_EndDate])) PIV

Answer 4

Use UNPIVOT & PIVOT like this:
Test data:
DECLARE #t table
(User1 varchar(20),Feature char(2),StartDate date,EndDate date)
INSERT #t values
('Pete','F1','2015/1/1 ','2015/2/1'),
('Pete','F2','2015/3/1 ','2015/4/1'),
('John','F1','2015/5/1 ','2015/6/1'),
('John','F2','2015/7/1 ','2015/8/1')
Query:
;WITH CTE AS
(
SELECT User1, date1, Feature + '_' + Seq cat
FROM #t as p
UNPIVOT
(date1 FOR Seq IN
([StartDate], [EndDate]) ) AS unpvt
)
SELECT * FROM CTE
PIVOT
(MIN(date1)
FOR cat
IN ([F1_StartDate],[F1_EndDate],[F2_StartDate],[F2_EndDate])
) as p
Result:
User1 F1_StartDate F1_EndDate F2_StartDate F2_EndDate
John 2015-05-01 2015-06-01 2015-07-01 2015-08-01
Pete 2015-01-01 2015-02-01 2015-03-01 2015-04-01