Question

I am working on an sql server 2008 database.

I have a table like this”

Id     Year    Series  Value
----+------+--------+------
1     1990    a       1.5
1     1990    b       1.6
1     1990    c       1.7
1     1991    a       1.8
1     1991    b       1.9
1     1991    c       2.5

Is there a query that can select the values and return them like this?

Year    a     b        c
------+------+--------+------
1990    1.5    1.6      1.7
1991    1.8    1.9      2.5

Thanks a lot for any help.

Answer 1

If series is fixed to a,b,c you can do this:

CREATE TABLE #t (Id    INT,  Year  INT,  
    Series VARCHAR(5), Value DECIMAL(10,1))
INSERT #t
VALUES
(1,     1990,    'a',       1.5),
(1,     1990,    'b',       1.6),
(1,     1990,    'c',       1.7),
(1,     1991,    'a',       1.8),
(1,     1991,    'b',       1.9),
(1,     1991,    'c',       2.5)

SELECT  pvt.Year,
        pvt.a,
        pvt.b,
        pvt.c
FROM    #t
PIVOT (
    MIN(Value) FOR Series IN ([a], [b], [c])
) pvt

If there would be other values you can use dynamic pivot:

DECLARE @series VARCHAR(100) = 
    STUFF(( SELECT  DISTINCT ',[' + Series + ']'
            FROM    #t
            FOR     XML PATH(''))
            ,1, 1, '')

DECLARE @query VARCHAR(2000) = '
SELECT  pvt.Year, ' + @series +'
FROM    #t
PIVOT (
    MIN(Value) FOR Series IN (' + @series + ')
) pvt
';

EXEC(@query)

In a scenario with fixed series, there is also possibility with CROSS JOIN:

SELECT  a.Year, 
        MAX(CASE WHEN a.Series = 'a' THEN a.Value END) a,
        MAX(CASE WHEN a.Series = 'b' THEN a.Value END) b,
        MAX(CASE WHEN a.Series = 'c' THEN a.Value END) c
FROM    #t a
CROSS   JOIN #t b
GROUP   BY a.Id, a.Year
ORDER   BY a.Year