Getting the last item in a "group by" query?

[Esbach, Brandon]

There is likely a blindingly obvious solution to this, I need to do a
group by expression in my query and get the latest row based on a date
field in the same table.  
Is this even possible, and any tips on how to do that?

Example of data and query:

-------
Table: 
=(pseudo table based on origional, trimmed)=
'id', 'bigint(20)', '', 'PRI', '', 'auto_increment'
'date', 'datetime', '', '', '0000-00-00 00:00:00', ''
'serial_number', 'varchar(25)', '', '', '', ''
'pass', 'varchar(6)', '', '', 'false', ''
=
SELECT 
         t.pass, t.id
FROM 
        theTable t group by t.serial_number
-------
I have tried putting a sort into the query like so:
SELECT 
         t.pass, t.id
FROM 
        theTable t 
GROUP BY
        t.serial_number
ORDER BY
        t.date desc 


Which naturally only sorts the resulting rows by date.