your SQL structure is good...
now what may be wrong could be one hundred things: empty table, no table named object_id, etc.
if you are using php to connect: make sure you are testing your commands every step of the way: db connection, db selection, query, number of returned rows...chances are, one of these things may have failed before you even could look at the results.
if you post your code, I'll be able to help more.
Thanks.