Simple

SELECT * FROM gallery2 WHERE topic_id="1819107" UNION SELECT * FROM gallery2 WHERE topic_id="451765" UNION SELECT * FROM gallery2 WHERE topic_id="1523114" UNION SELECT * FROM gallery2 WHERE topic_id="1177136" UNION SELECT * FROM gallery2 WHERE topic_id="1073606" UNION SELECT * FROM gallery2 WHERE topic_id="1380768" UNION SELECT * FROM gallery2 WHERE topic_id="1110301" UNION SELECT * FROM gallery2 WHERE topic_id="721326" UNION SELECT * FROM gallery2 WHERE topic_id="1578218" UNION SELECT * FROM gallery2 WHERE topic_id="1368917" UNION SELECT * FROM gallery2 WHERE topic_id="570497" UNION SELECT * FROM gallery2 WHERE topic_id="461734" UNION SELECT * FROM gallery2 WHERE topic_id="574016" UNION SELECT * FROM gallery2 WHERE topic_id="181603" UNION SELECT * FROM gallery2 WHERE topic_id="1012852" UNION SELECT * FROM gallery2 WHERE topic_id="1167312"