MySQL string comparison without operator inconsistency on the same server?

Programming in mysql: MySQL string comparison without operator inconsistency on the same server? on newest questions tagged mysql – Stack Overflow

I found what is to me a really weird phenomenon. In my MySQL server which is version 5.0.92, I use a query as follows:

SELECT IF(thumb, thumb, image) AS thumb FROM blog WHERE id = 200;

Because I want to get the thumb value if it is not empty, otherwise the image value. Now in one database on this server, this works perfectly fine, just the way I want it to. But on another database on the exact same server, thumb always evaluates to false, even it is not empty, and the value for image is always selected.

I know that I can use thumb != '' and that does work on both databases but please someone tell me how this happened? Is this some kind of database-specific setting?

source: http://stackoverflow.com/questions/11880198/mysql-string-comparison-without-operator-inconsistency-on-the-same-server
Programming in mysql: programming-in-mysql