mysql> SELECT DISTINCT thread_id, subject FROM msg WHERE apr=1 ORDER BY post_stamp DESC LIMIT 10;  

ERROR 3065 (HY000): Expression #1 of ORDER BY clause is not in the SELECT list, referencing column 'msg.post_stamp' which is not in the SELECT list; this is incompatible with DISTINCT;

SELECT DISTINCT thread_id, subject
FROM ( SELECT thread_id, subject 
       FROM msg 
       WHERE apr=1 
       ORDER BY post_stamp DESC 
       LIMIT <something larger enough to then get 10 distinct> )
LIMIT 10; 

mysql> SELECT DISTINCT thread_id, subject FROM (SELECT thread_id, subject FROM msg WHERE apr=1 ORDER BY post_stamp DESC LIMIT 30) LIMIT 10;
ERROR 1248 (42000): Every derived table must have its own alias

mysql> SELECT DISTINCT thread_id, subject FROM (SELECT thread_id, subject FROM msg WHERE apr=1 ORDER BY post_stamp DESC LIMIT 50) x LIMIT 10;
+-----------+--------------------------------------------------------------------+
| thread_id | subject                                                            |
+-----------+--------------------------------------------------------------------+
|    208718 | Re: New server migration                                           |
|    208719 | Re: ORDER BY clause is not in SELECT list                          |
|    208717 | Re: Help Needed in Calculation Logic function                      |
|    208719 | ORDER BY clause is not in SELECT list                              |
|    208718 | New server migration                                               |
|    208714 | Re: dense_rank() in formula column                                 |
|    208717 | Help Needed in Calculation Logic function                          |
|    208716 | Re: Find out the column values based on primary key from one table |
|    208716 | Find out the column values based on primary key from one table     |
|    208265 | Re: FCBGuard or USB security token login AS SYSDBA                 |
+-----------+--------------------------------------------------------------------+