如何在SQL Server的選擇列中寫入條件？

Question

我有一個類似的Select語句

select AVG(CAST(DATEDIFF(Day,CreatedDate,FirstTouchDate) AS BIGINT) else null end) AS avgdaystofirstattempt,
       AVG(CAST(DATEDIFF(Day,CreatedDate,Completeddate) AS BIGINT)) AS AvgDaystoComplete
from Table1

我如何在選擇本身而不是where子句中為avgdaystofirstattempt-FirstTouchdate列的條件寫不像'％1900％'的條件。

提前致謝

Answer 1

您可以使用CASE選擇性地將數據包含在聚合語句中。 您的問題還不清楚，但是我想您需要這樣的東西：

SELECT AVG(
             CASE 
               WHEN DATEDIFF(Day,CreatedDate,FirstTouchDate) < 1900 THEN NULL
               ELSE CAST(DATEDIFF(Day,CreatedDate,FirstTouchDate) AS BIGINT)
               END
           ) AS avgdaystofirstattempt,
       AVG(CAST(DATEDIFF(Day,CreatedDate,Completeddate) AS BIGINT)) AS AvgDaystoComplete
FROM Table1