SELECT citatum_text.id AS id, citatum_text.`text` AS `text`, citatum_text.author AS author, citatum_tag.tag AS tag FROM citatum_text
LEFT JOIN citatum_tag ON citatum_text.id = citatum_tag.citatum_id
JOIN citatum_tag AS t2 ON citatum_text.id = t2.citatum_id
WHERE t2.tag='отношения';