Problem with "order by"

[Bradley Munz]

Hi there,

I have a bizarre problem with "order by" usage in Derby sql. Below is a
simple table from that contains some availability data:

CREATE TABLE agent_availabilty_rt
agent_id integer,
username varchar(30) UNIQUE, 
reserved tintyint DEFAULT 1,
availtime bigint,
PRIMARY KEY(agent_id))

I need to extract this data and "join" it with another table (which
isn't of importance in this email):

select agent_avail.username,agent_avail.availtime 
from (
    select username,agent_id,availtime 
    from agent_availabilty_rt 
    where agent_availabilty_rt.reserved = 0 
    order by agent_availabilty_rt.availtime asc
) agent_avail 

For some reason derby doesn't like this bit of sql (However it does work
on other DBs like postgres). If I remove the "order by" I.e:

select agent_avail.username,agent_avail.availtime 
from (
    select username,agent_id,availtime 
    from agent_availabilty_rt 
    where agent_availabilty_rt.reserved = 0 
    //order by agent_availabilty_rt.availtime asc
) agent_avail 

it works fine. 

Is there something I'm missing here?

Thanks in advance.
Brad Munz