query problem with null

[Richard Reina]

 When I do the following query:

SELECT * FROM geo_trivia WHERE city IS NULL;

certain columns that DO have 'NULL' value for city and not a '' (blank)
value do not show up.
I have even gone to the extent of reseting these records value as ='NULL'
with UPDATE and they are still are not selected when I run the above
query.  Can anyone help?