sql - 左连接充当内部连接？

Question

我有以下查询:

   SELECT DISTINCT t.productid as Prod_id,
   EXTRACT(week from t.dt) as WEEK,
   COUNT(pv.productid) as PageViews,
   COUNT(t.productid) as orders, 
   COUNT(t.productid)/COUNT(DISTINCT(pv.loadid)) as Conversion,
   AVG(t.price) avg_price,
   MAX(pv.numreviews) max_numreviews,
   MIN(pv.numreviews) min_numreviews,
   AVG(pv.numreviews) avg_numreviews,
   COUNT( DISTINCT pv.bvsid ) sessions
   FROM PageView pv LEFT OUTER JOIN Transaction t ON t.productid = pv.productid 
   AND t.dt BETWEEN '2014-06-06' AND '2014-06-18' AND ( lower(t.currency) = 'usd' OR lower(t.country) IN ('us', 'usa', 'united states') )
   WHERE pv.dt BETWEEN '2014-06-06' AND '2014-06-18'
   AND pv.client ='abc' AND lower(pv.type) = 'product'
   GROUP BY WEEK, Prod_id
   ORDER BY WEEK asc;

它为 PageViews 和 Orders 提供相同的值，基本上只采用常见的 productid。我想要页面浏览量和订单的正确值，非常感谢这方面的帮助。

Answer 1

表达式:

COUNT(pv.productid) as PageViews,
COUNT(t.productid) as orders, 

统计两个字段的非NULL值。如果它们相同，则所有记录都匹配。但是，我怀疑您想要:

COUNT(pv.productid) as PageViews,
COUNT(distinct t.productid) as orders, 

此外，当您有 group by 子句时，您不应使用 select distinct。