[英]I created a column in the select; how do i use it in the where?
我在select語句( DaysSinceCheck
)中創建了一個列。
如何在WHERE
子句中使用它?
SELECT DISTINCT
Name,
(DATEDIFF(D, max(lastDaTe), GETDATE())) AS DaysSinceCheck
FROM
event_table
WHERE
cust = 'usa'
AND ((DATEDIFF(D, max(lastDaTe), GETDATE()))) <= 2
GROUP BY
Name
收到錯誤:
除非聚集在HAVING子句或選擇列表中包含的子查詢中,並且聚集的列是外部引用,否則聚集可能不會出現在WHERE子句中。
您可以使用HAVING子句測試聚合函數的值。
...
WHERE cust = 'usa'
GROUP BY Name
HAVING ((DATEDIFF(D, max(lastDaTe), GETDATE()))) <= 2
HAVING解決方案運行良好...另一種方法是使用CTE將事物分成兩部分,如下所示:
WITH NameAndDays AS (
SELECT DISTINCT Name,
(DATEDIFF(D, max(lastDaTe), GETDATE())) AS DaysSinceCHECK
FROM event_table
WHERE cust = 'usa'
GROUP BY Name
) SELECT *
FROM NameAndDays
WHERE DaysSinceCHECK <= 2
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