how can use multiline SQL command block in drupal?

hi all
db_query just allow one line sql command to run
i need to run this sql command:

db_query('
SET @nid = ( SELECT node.nid
FROM content_type_news
INNER JOIN node ON node.nid = content_type_news.nid
WHERE content_type_news.field_home_position_value =0
ORDER BY created DESC
LIMIT 1 ) ;
update content_type_news inner join node on node.nid=content_type_news.nid SET field_home_position_value =1 where node.nid=@nid;
');

how can i do that?