I have a question about this fiddle:


Is it ever possible to get -1 as the result of this query? 
I think no, right because potato can be either null or not null and the case covers both scenario? 

sql server 11 

Top Answer
You are correct.

The CASE conditional expression can evaluate to either 1 or 0, never to a NULL.

The encapsulating ISNULL function will always see a concrete value, `1` or `0`, and so will never return `-1`.

If you explain what you are trying to achieve with this code that doesn't seem to work for you, we may be able to offer some advice.
Trying to understand an isnull expression
@Ami I edited the answer. The isnull can return 1 or 0, whatever the case returns. It is true that it can never return -1.
Lamak replying to Anonymous
that fiddle seems to work fine?
the real code is not much more complex than this. just trying to understand if I am missing something... 
have you tried `set @potato = null;` and seeing what is returned?  Also, try removing the `set` statement altogether.  This seems like a pretty easy thing to prove.  If you have a more complex scenario in reality, please post that.  Cheers!