Requête mySQL pour additionner le montant en colonnes (mois)

Cette requête devrait vous donner le résultat requis.

SELECT category
  ,tran_type
  ,SUM(IF(month(date) = 1,ABS(amount),0)) as jan_total
  ,SUM(IF(month(date) = 2,ABS(amount),0)) as feb_total
  ,SUM(IF(month(date) = 3,ABS(amount),0)) as mar_total
  ,SUM(IF(month(date) = 4,ABS(amount),0)) as apr_total
  ,SUM(IF(month(date) = 5,ABS(amount),0)) as may_total
  ,SUM(IF(month(date) = 6,ABS(amount),0)) as jun_total
  ,SUM(IF(month(date) = 7,ABS(amount),0)) as jul_total
  ,SUM(IF(month(date) = 8,ABS(amount),0)) as aug_total
  ,SUM(IF(month(date) = 9,ABS(amount),0)) as sep_total
  ,SUM(IF(month(date) = 10,ABS(amount),0)) as okt_total
  ,SUM(IF(month(date) = 11,ABS(amount),0)) as nov_total
  ,SUM(IF(month(date) = 12,ABS(amount),0)) as dec_total
 FROM transactions
 WHERE YEAR(date) = '2011'
 GROUP BY category, tran_type

N'oubliez pas de filtrer par année si vous ne voulez pas avoir de problèmes.