Sql 在同一查询中的不同筛选器上选择聚合

这是我的问题

  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

它起作用了；但是，我需要过滤平均值和STDEV，其中testfreq>0，但我需要不过滤计数（*）

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

您应该能够在聚合中使用类似以下内容的

CASE

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

我不知道为什么需要将这些值作为varchar，是否有理由需要将这些值转换为

varchar

我只想让这些值保持原样：

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

---

为什么要将结果转换为字符串？测试频率的类型是什么？