本文介绍了检查 SQL Server 中列的值是否为空的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
不敢相信我坚持这个，但我如何检查我返回的值在 select 语句中是否为空
Can't believe I am stuck with this but how can I check that value I am returning is null in select statement
IF EXISTS(SELECT TU.Tagged FROM TopicUser TU
WHERE TU.TopicId = @TopicId and TU.UserId = @UserId)
BEGIN
--do stuff
END
TU.Tagged 的值是 NULL 但它确实进入了条件.心目中它不存在.
The value of TU.Tagged is NULL but yet it does go into the condition. In mind it does not exist.
推荐答案
看起来你需要这样的东西:
It looks like you need something like:
IF EXISTS(SELECT TU.Tagged
FROM TopicUser TU
WHERE TU.TopicId = @TopicId
AND TU.UserId = @UserId
AND TU.Tagged IS NOT NULL)
BEGIN
--do stuff
END
否则，您只会检查是否存在符合您条件的记录，但这些记录在 TU.Tagged 列中可能具有 NULL 值.
Otherwise, you're checking only if records meeting your criteria exist, but those records could have a NULL value in the TU.Tagged column.
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