Result of comparing null

[chibbie23]

I have a column on my table which may contain yes,no or null. I have learned that comparing null values will always result to FALSE. I have created a condition in one of my queries which is something like this:

Where column1 <> 'Yes'

I need to display entries where column1 is either 'No' or is null. Now my question is, would the null values satisfy this condition?

I know i can just do something like:

where isnull(column1,'') <> 'Yes'

or:

where column1 = 'No' OR column1 is null

I just want to know the reason behind the result. Thanks

[ck9663]

I'm not sure where you learn that comparing a NULL value to a non-NULL value will always return FALSE. Depending on the structure of your comparison, it will not always return FALSE, but UNKNOWN. Here, start from here.


Happy Coding!!!


~~ CK

[chibbie23]

So now it really is a three valued logic, true, false and unknown. meaning null is never equal or unequal to anything, because the result is unknown.

Thanks!

[ck9663]

Yes. You cannot check if a value is equal to NULL. But you can check if a value is NULL.

Happy Coding!!!


~~ CK