如何在 SQL 钻取查询中检查表中的列退出

问题描述

SELECT t1.customerinformation.customerid AS CustomerId
FROM EndUserNotificationHistoryEvent t1
WHERE t1.operationType <> 'DELETE';

在上面的查询中，仅当表中存在 operationType 列时才应执行条件。如果在不需要条件的情况下不存在 operationType 列。

解决方法

对于此特定查询，您可以使用：

SELECT t1.customerInformation.customerid AS CustomerId
FROM EndUserNotificationHistoryEvent t1
WHERE t1.operationType <> 'DELETE' OR t1.operationType IS NULL;

向 where 子句添加 IS NULL 检查将有效关闭删除检查，如果列是 NULL。

,

试试这个：

SELECT t1.customerInformation.customerid AS CustomerId
FROM EndUserNotificationHistoryEvent t1
WHERE (t1.operationType <> 'DELETE' OR t1.operationType IS NULL)

,

除了布尔运算，另一种方法是使用 COALESCE 如下：

SELECT T1.CUSTOMERINFORMATION.CUSTOMERID AS CUSTOMERID
  FROM ENDUSERNOTIFICATIONHISTORYEVENT T1
 WHERE COALESCE(T1.OPERATIONTYPE,'NOT DELETE') <> 'DELETE'; 
-- WHEN T1.OPERATIONTYPE IS NULL,CONDITION WILL BE ALWAYS TRUE