Maybe now is a good moment to go through the Basic debugging checklist. Consider step 2, printing the contents of your variables instead of guessing at what they might contain, and step 4, using Data::Dumper.

Also, you haven't told us what database server and what version you are using, and what ->table_info returns. From your usage of LIMIT 0, I assume that it is some kind of MySQL but I prefer not to guess.