Question

I am using following query which works fine for me except one problem

SELECT f.period                            AS month,
       SUM(p.revenue * ((100-q.rate)/100)) AS revenue,
       COUNT(DISTINCTq.label)              AS tot_stmt 
FROM files f, reports p, rates q,albums a
WHERE f.period IN ('2010-06-01','2010-05-01','2010-04-01','2010-03-01') 
  AND f.period_closed = TRUE
  AND q.period = f.period
  AND a.id = q.album_id
  AND p.file_id = f.id
  AND p.upc = a.upc
  AND p.revenue IS NOT NULL
GROUP BY month
ORDER BY month DESC;

O/P =>

month            revenue  
  tot_stmt

2010-06-01     10.00         2

2010-05-01     340.47       2

I want result like following:

month            revenue  
  tot_stmt

2010-06-01     10.00         2

2010-05-01     340.47       2
2010-04-01     0.00      
    0
2010-03-01     0.00  
        0

Answer 1

SELECT f.period                                       AS month,
       IFNULL(SUM(p.revenue * ((100-q.rate)/100)), 0) AS revenue,
       COUNT(DISTINCT q.label)                        AS tot_stmt 
FROM files f 
     LEFT JOIN reports p ON f.id = p.file_id
     LEFT JOIN rates q ON f.period = q.period
     LEFT JOIN albums a ON q.album_id = a.id AND p.upc = a.upc
WHERE f.period IN ('2010-06-01','2010-05-01','2010-04-01','2010-03-01') 
  AND f.period_closed = TRUE
GROUP BY month
ORDER BY month DESC;

Explanations:

• rewritten the conditions to have JOIN clauses
• COUNT(column) returns 0 if all aggregated records have value
  NULL in that column
• SUM(column) returns NULL if all aggregated records have value
  NULL in that column
• you also need to allow p.revenue to be NULL (dropped that
  criteria)

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Note

You don’t seem to be getting anything from the albums table so you can take it out.