mysql> select topic_id from topics;
+ ----------+
 
| topic_id |
+ ----------+
 
|         1  |
|         2  |
|         3  |
|       105  |
|       706  |
+ ----------+
 
 5  rows in set ( 0 . 01  sec)

mysql> select topics.topic_id from topics LEFT JOIN vote USING (topic_id) GROUP
BY vote.topic_id;
+ ----------+
 
| topic_id |
+ ----------+
 
|       105  |
|         1  |
|         2  |
|         3  |
+ ----------+
 
 4  rows in set ( 0 . 00  sec)

create table topics (
	topic_id integer unsigned not null primary key auto_increment,
	login char( 255 ),
	title char( 255 ),
	date timestamp not null,
	size integer unsigned not null,
	ip char( 15 ),
	section char( 15 ),
	text mediumtext);


create table vote (
	vote_id integer unsigned not null primary key auto_increment,
	topic_id integer not null,
	date timestamp not null,
	vote integer,
	ip char( 15 ));