SQL 仅将 where 子句应用于一个字段

Question

我想将 WHERE 子句应用于我的选择查询的一个字段。互联网告诉我在选择字段的行中使用 CASE WHEN，然后删除 where 子句。但后来有人告诉我，我的“selected non aggregate values must be part of the associated group."

原始查询如下所示：

SELECT 
    CAST(EVENT_TIMESTAMP AS DATE) AS Date1, 
    COUNT(DISTINCT EMAIL) END AS Subs, 
    SUM(DWELL_MINUTES) AS Dwell
FROM VwNIMEventFct
INNER JOIN VwNIMUserDim ON VwNIMUserDim.NIM_USER_ID = VwNIMEventFct.NIM_USER_ID
INNER JOIN TmpNIMSalesForceDB ON VwNIMUserDim.USER_EMAIL_ADDRESS = EMAIL


WHERE Date1 >= '2013-11-01'
// The problem is here, in the AND clause
AND (SUBSCRIPTION_END_DATE > VwNIMEventFct.EVENT_TIMESTAMP OR SUBSCRIPTION_END_DATE 
IS NULL)

GROUP BY Date1
ORDER BY Date1

然后我在做一些搜索后更改了查询：

  SELECT 
    CAST(EVENT_TIMESTAMP AS DATE) AS Date1, 
    CASE WHEN (SUBSCRIPTION_END_DATE > Date1 OR SUBSCRIPTION_END_DATE IS NULL)
        THEN COUNT(DISTINCT TmpNIMSalesForceDB.EMAIL) END AS Subs, 
    SUM(VwNIMEventFct.DWELL_MINUTES) AS Dwell
    FROM RDMAVWSANDBOX.VwNIMEventFct
   INNER JOIN VwNIMUserDim ON VwNIMUserDim.NIM_USER_ID = VwNIMEventFct.NIM_USER_ID
   INNER JOIN TmpNIMSalesForceDB ON VwNIMUserDim.USER_EMAIL_ADDRESS = EMAIL
   WHERE Date1 >= '2013-11-01'
   GROUP BY Date1
   ORDER BY Date1

我想选择： 1）查询中的“Date1”日期，然后， 2) 对于每个日期，SUBSCRIPTION_END_DATE 为 NULL 或将来（大于 Date1）的不同电子邮件地址的计数， 3）一个字段的总和（我这里很好）

第 2 点怎么做？

根据答案编辑： 选择查询的这一部分是否忽略并因此不计算空白记录 SUBSCRIPTION_END_DATE 为空？

SELECT 
    COUNT(DISTINCT CASE  WHEN TmpNIMSalesForceDB.SUBSCRIPTION_END_DATE > Date1 OR TmpNIMSalesForceDB.SUBSCRIPTION_END_DATE IS NULL
             THEN TmpNIMSalesForceDB.EMAIL END) AS Subs, 

我需要计算 SUBSCRIPTION_END_DATE 为空白/null 或这些日期在 Date1 之后的所有记录。

Answer 1

您需要将 CASE 语句放在 COUNT 中，而不是相反，因为它需要针对每一行进行评估（该行应该属于哪种情况），然后在每个组中聚合（该组中有多少行属于非空组）。

 COUNT(DISTINCT CASE WHEN (SUBSCRIPTION_END_DATE > Date1 OR SUBSCRIPTION_END_DATE IS NULL)
    THEN TmpNIMSalesForceDB.EMAIL END) AS Subs

COUNT 将忽略 CASE 语句中缺少 ELSE 子句隐式留下的 NULL，因此只计算满足条件的行中不同的 EMAIL 值。

Answer 2

将case 语句放在count 函数内。

SELECT 
    CAST(EVENT_TIMESTAMP AS DATE) AS Date1, 
    COUNT(DISTINCT(CASE 
             WHEN SUBSCRIPTION_END_DATE > Date1 OR SUBSCRIPTION_END_DATE IS NULL
             THEN TmpNIMSalesForceDB.EMAIL END)) AS Subs, 
    SUM(VwNIMEventFct.DWELL_MINUTES) AS Dwell
FROM RDMAVWSANDBOX.VwNIMEventFct
    INNER JOIN VwNIMUserDim 
        ON VwNIMUserDim.NIM_USER_ID = VwNIMEventFct.NIM_USER_ID
    INNER JOIN TmpNIMSalesForceDB 
        ON VwNIMUserDim.USER_EMAIL_ADDRESS = EMAIL
WHERE Date1 >= '2013-11-01'
GROUP BY Date1
ORDER BY Date1