[ILUG-Webdev] MySQL NULL problem

[kverens]

I have a line of SQL which I thought was simple:
update photographers set state=town where state is null and 
country='Ireland'; 

this returns 0 changes. 

strangely, the below returns 187 results:
select * from photographers where state is null and country='Ireland'; 

town is plain text, as is state and country. 

any ideas what I'm doing wrong? 

Kae