SQL error

Error 1, 'Can't create/write to file '/var/tmp/#sql_721_0.MAI' (Errcode: 28)'

at /var/www/trinova/data/www/trinova.ru/inc/db_sql.php:41

Query: SELECT ip.project_id, ip.img, p.segment_id, p.name_ru as name, p.preview_ru as preview, p.url_ru as url FROM img2project AS ip LEFT JOIN project AS p ON p.id = ip.project_id WHERE p.published_ru=1 AND p.segment_id='12' and p.id<>'57' ORDER BY RAND() LIMIT 12;