ひろせといいます

MySQL 4 以上限定ですが、(UNION ALLじゃなくて) UNION は DISTINCT と同じ
作用を持っているので、これを利用すればうまくいくかもしれません。

(select question_no from test order by create_date desc)
union
(select question_no from test where 1<0)
limit 10;

もしくはダミーselectなしで、

(select question_no from test order by create_date desc) limit 10;

でもいけます。

mysql> select * from q order by o desc;
+------+------+
| n    | o    |
+------+------+
|    1 |  101 |
|    1 |  100 |
|   10 |   92 |
|   10 |   91 |
|   10 |   90 |
|   20 |   82 |
|   20 |   81 |
|   20 |   80 |
|   40 |   80 |
|   30 |   70 |
+------+------+
10 rows in set (0.00 sec)

mysql> select distinct n from q order by o desc limit 3;
+------+
| n    |
+------+
|    1 |
|   10 |
|   40 |
+------+
3 rows in set (0.00 sec)

mysql> (select n from q order by o desc) limit 3;
+------+
| n    |
+------+
|    1 |
|   10 |
|   20 |
+------+
3 rows in set (0.00 sec)

ではでは

-- 
ひろせ
http://www.irori.org/