ifステートメントを使用したSQLクエリ

クエリは次のように記述します：

SELECT o.name AS offer, COUNT(c.id) AS clicks, 
  SUM( IF(c.conversionDate IS NOT NULL, o.commission, NULL) ) AS revenue 
FROM offers o JOIN clicks c ON (c.offerID=o.ID)
GROUP BY o.ID;

別の解決策がありますが、がないオファー 変換されたクリックはクエリ結果に表示されません：

SELECT o.name AS offer, COUNT(c.id) AS clicks, 
  SUM(o.commission) AS revenue 
FROM offers o JOIN clicks c 
  ON (c.offerID=o.ID AND c.conversionDate IS NOT NULL)
GROUP BY o.ID;