SQL Pivoting or Transposing or ... column to row? - sql

Question

I have a question and this looks way better in SQLfiddle:
http://www.sqlfiddle.com/#!3/dffa1/2
I have a table with multirows for each user with datestamp and test results and i would like to transpose or pivot it into one line result as follows where each user has listed all time and value results:
USERID PSA1_time PSA1_result PSA2_time PSA2_result PSA3_time PSA3_result ...
1 1999-.... 2 1998... 4 1999... 6
3 1992... 4 1994 6
4 2006 ... 8
Table below:
CREATE TABLE yourtable
([userid] int, [Ranking] int,[test] varchar(3), [Date] datetime, [result] int)
;
INSERT INTO yourtable
([userid], [Ranking],[test], [Date], [result])
VALUES
('1', '1', 'PSA', 1997-05-20, 2),
('1', '2','PSA', 1998-05-07, 4),
('1', '3','PSA', 1999-06-08, 6),
('1', '4','PSA', 2001-06-08, 8),
('1', '5','PSA', 2004-06-08, 0),
('3', '1','PSA', 1992-05-07, 4),
('3', '2','PSA', 1994-06-08, 6),
('4', '1','PSA', 2006-06-08, 8)
;

Answer 1

Since you want to PIVOT two columns my suggestion would be to unpivot the date and result columns first, then apply the PIVOT function.
The unpivot process will convert the two columns date and result into multiple rows:
select userid,
col = test +'_'+cast(ranking as varchar(10))+'_'+ col,
value
from yourtable t1
cross apply
(
select 'time', convert(varchar(10), date, 120) union all
select 'result', cast(result as varchar(10))
) c (col, value)
See Demo. This will give you a result:
| USERID | COL | VALUE |
--------------------------------------
| 1 | PSA_1_time | 1997-05-20 |
| 1 | PSA_1_result | 2 |
| 1 | PSA_2_time | 1998-05-07 |
| 1 | PSA_2_result | 4 |
| 1 | PSA_3_time | 1999-06-08 |
Now that you have the data in this format, then you can apply pivot to get the max/min value for each item in col:
If you have a limited number of columns, then you can hard-code the query:
select *
from
(
select userid,
col = test +'_'+cast(ranking as varchar(10))+'_'+ col,
value
from yourtable t1
cross apply
(
select 'time', convert(varchar(10), date, 120) union all
select 'result', cast(result as varchar(10))
) c (col, value)
) d
pivot
(
max(value)
for col in (PSA_1_time, PSA_1_result,
PSA_2_time, PSA_2_result,
PSA_3_time, PSA_3_result,
PSA_4_time, PSA_4_result,
PSA_5_time, PSA_5_result)
) piv;
See SQL Fiddle with Demo
If you have unknown columns, then you will need to use dynamic SQL:
DECLARE #cols AS NVARCHAR(MAX),
#query AS NVARCHAR(MAX)
select #cols = STUFF((SELECT ',' + QUOTENAME(test +'_'+cast(ranking as varchar(10))+'_'+ col)
from yourtable
cross apply
(
select 'time', 1 union all
select 'result', 2
) c (col, so)
group by test, ranking, col, so
order by Ranking, so
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set #query = 'SELECT userid,' + #cols + '
from
(
select userid,
col = test +''_''+cast(ranking as varchar(10))+''_''+ col,
value
from yourtable t1
cross apply
(
select ''time'', convert(varchar(10), date, 120) union all
select ''result'', cast(result as varchar(10))
) c (col, value)
) x
pivot
(
max(value)
for col in (' + #cols + ')
) p '
execute sp_executesql #query;
See SQL Fiddle with Demo. Both versions will give a result:
| USERID | PSA_1_TIME | PSA_1_RESULT | PSA_2_TIME | PSA_2_RESULT | PSA_3_TIME | PSA_3_RESULT | PSA_4_TIME | PSA_4_RESULT | PSA_5_TIME | PSA_5_RESULT |
------------------------------------------------------------------------------------------------------------------------------------------------------
| 1 | 1997-05-20 | 2 | 1998-05-07 | 4 | 1999-06-08 | 6 | 2001-06-08 | 8 | 2004-06-08 | 0 |
| 3 | 1992-05-07 | 4 | 1994-06-08 | 6 | (null) | (null) | (null) | (null) | (null) | (null) |
| 4 | 2006-06-08 | 8 | (null) | (null) | (null) | (null) | (null) | (null) | (null) | (null) |