Question

I´m currently struggling to get this to work.

SELECT        Y, SUM(N) AS sumDK, NULL AS sumFI, NULL AS sumNO, NULL AS sumSE
FROM            stat
WHERE        (C = 'Denmark')
GROUP BY Y
UNION ALL
SELECT        Y, NULL AS sumDK, SUM(N) AS sumFI, NULL AS sumNO, NULL AS sumSE
FROM            stat
WHERE        (C = 'Finland')
GROUP BY Y
UNION ALL
SELECT        Y, NULL AS sumDK, NULL AS sumFI, SUM(N) AS sumNO, NULL AS sumSE
FROM            stat
WHERE        (C = 'Norway')
GROUP BY Y
UNION ALL
SELECT        Y, NULL AS sumDK, NULL AS sumFI, NULL AS sumNO, SUM(N) AS sumSE
FROM            stat
WHERE        (C = 'Sweden')
GROUP BY Y

This query gives me a matrix like this:

Y | sumDK | sumFI | sumNO | sumSE
----------------------------------
2011| 25 | NULL | NULL | NULL 
2012| 5 | NULL | NULL | NULL 
2011| NULL | 18 | NULL |NULL 
2012| NULL | 5 | NULL |NULL 
......

How can I perform a query that only returns the fields NOT NULL?
Thanks in advance!

Answer 1

go through the table once, and create it as a cross-tab by summing the match of respective columns

select
      Y,
      SUM( IIF( C = 'Denmark', N, 0 )) as SumDenmark,
      SUM( IIF( C = 'Finland', N, 0 )) as SumFinland,
      SUM( IIF( C = 'Norway', N, 0 )) as SumNorway,
      SUM( IIF( C = 'Sweden', N, 0 )) as SumSweden,
      sum( N ) totalSumValue,
      count(*) totalEntries
   FROM 
      STAT
   WHERE
      C IN ( 'Denmark', 'Finland', 'Norway', 'Sweden' )
  GROUP BY 
      Y