sql - 在同一查询中选择不同过滤器上的聚合

Question

这是我的查询

  SELECT
    client_id,
   TimesTested,
    CAST(COUNT(*) AS varchar(30)) AS count,
    CAST(AVG(testfreq) as varchar(30)) as TestFreq,
    CAST(STDEV(TestFreq) as varchar(30)) Stdv
  FROM counted
  GROUP BY
    client_id,
    TimesTested

有用; 但是，我需要过滤 testfreq>0 的 AVG 和 STDEV，但我需要不过滤 count(*)。

最接近的是：

  SELECT
    client_id,
   TimesTested,
    CAST(COUNT(*) AS varchar(30)) AS count,
    CAST(AVG(testfreq) as varchar(30)) as TestFreq,
    CAST(STDEV(TestFreq) as varchar(30)) Stdv
  FROM counted
  where testfreq>0  --however I don't want this filtered applied to count(*)
  GROUP BY
    client_id,
    TimesTested

非常感谢您的指导！

Answer 1

您应该能够CASE在聚合中使用类似于以下内容的语句：

SELECT client_id,
   TimesTested,
   CAST(COUNT(*) AS varchar(30)) AS count,
   CAST(AVG(case when testfreq>0 then testfreq end) as varchar(30)) as TestFreq,
   CAST(STDEV(case when testfreq>0 then TestFreq end) as varchar(30)) Stdv
FROM counted
GROUP BY client_id,  TimesTested

我不确定为什么需要将这些值作为 varchars，是否有理由需要将这些值转换为varchar？

我将保持原样的值：

SELECT client_id,
   TimesTested,
   COUNT(*) AS count,
   AVG(case when testfreq>0 then testfreq end) as TestFreq,
   STDEV(case when testfreq>0 then TestFreq end) Stdv
FROM counted
GROUP BY client_id,  TimesTested