Q:

How to select features where attribute is not NULL?

I have an OS AddressBase shape file. One of the attributes is 'paoText'. It is either a text string like 'Anchor House' or is NULL. 
I want to extract all the records where there is a text string i.e. the attribute is not NULL.  
I have tried Advance search with paoText = NULL with the idea of inverting the result to get all those records that contain text i.e. a property name, but my search returns nill records.  
I know there are records with NULL in that attribute because I can see them. What am I doing wrong please?

A:

Have you tried
paoText is NULL

or
paoText is not NULL

