Check if a column's value is null in SQL Server

Question

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

The value of TU.Tagged is NULL but yet it does go into the condition. In mind it does not exist.

Answer 1

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

Otherwise, you're checking only if records meeting your criteria exist, but those records could have a NULL value in the TU.Tagged column.