Sql server SQL Server按日期进行选择和分组

我试图按产品分组，并根据datediff函数返回它们的平均使用时间

我的问题是：

SELECT products.productNameCommon, datediff(minute,history.timeOut, history.timeIn) as session
FROM FlexLM_history history
JOIN FlexLM_products products ON products.productID=history.productID
where products.productType = 'base' and history.timeIn is Not NULL
GROUP BY products.productNameCommon, datediff(minute,history.timeOut, history.timeIn)
ORDER BY products.productNameCommon

我的结果如下：

我真正需要的是：

productNameCommon | avgSession
----------------- | ----------
Product 1         | 20
Product 2         | 3.5
Product 3         | 18

---

您可以使用子查询和平均

SELECT Q.ProductNameCommon, AvgSession = AVG(Session) FROM
( --Your query
    SELECT products.productNameCommon, datediff(minute,history.timeOut, history.timeIn) as Session
    FROM FlexLM_history history
    JOIN FlexLM_products products ON products.productID=history.productID
    where products.productType = 'base' and history.timeIn is Not NULL
    GROUP BY products.productNameCommon, datediff(minute,history.timeOut, history.timeIn)
) as Q
group by Q.ProductNameCommon
order by Q.ProductNameCommon

---

您可以使用子查询和平均

SELECT Q.ProductNameCommon, AvgSession = AVG(Session) FROM
( --Your query
    SELECT products.productNameCommon, datediff(minute,history.timeOut, history.timeIn) as Session
    FROM FlexLM_history history
    JOIN FlexLM_products products ON products.productID=history.productID
    where products.productType = 'base' and history.timeIn is Not NULL
    GROUP BY products.productNameCommon, datediff(minute,history.timeOut, history.timeIn)
) as Q
group by Q.ProductNameCommon
order by Q.ProductNameCommon

---

如果将

datediff（）

从

分组中删除，并将
datediff（）
包装在所选列的
sum（）
中，会发生什么情况？ie:sum（datediff（））如果您从
分组中删除
datediff（）
，并将
datediff（）
包装在所选列的
sum（）
中，会发生什么情况？ie:sum（datediff（））几乎正确。只是错过了ABC.productNameCommon的
组
几乎正确。只是缺少ABC.productNameCommon的
组
SELECT Q.ProductNameCommon, AvgSession = AVG(Session) FROM
( --Your query
    SELECT products.productNameCommon, datediff(minute,history.timeOut, history.timeIn) as Session
    FROM FlexLM_history history
    JOIN FlexLM_products products ON products.productID=history.productID
    where products.productType = 'base' and history.timeIn is Not NULL
    GROUP BY products.productNameCommon, datediff(minute,history.timeOut, history.timeIn)
) as Q
group by Q.ProductNameCommon
order by Q.ProductNameCommon