I think you need some correction

SELECT * FROM gallery2 WHERE topic_id="1477026" UNION SELECT * FROM gallery2 WHERE topic_id="1821789" UNION SELECT * FROM gallery2 WHERE topic_id="989831" UNION SELECT * FROM gallery2 WHERE topic_id="1153842" UNION SELECT * FROM gallery2 WHERE topic_id="924179" UNION SELECT * FROM gallery2 WHERE topic_id="398464" UNION SELECT * FROM gallery2 WHERE topic_id="174828" UNION SELECT * FROM gallery2 WHERE topic_id="1363751" UNION SELECT * FROM gallery2 WHERE topic_id="30886" UNION SELECT * FROM gallery2 WHERE topic_id="177594" UNION SELECT * FROM gallery2 WHERE topic_id="73741" UNION SELECT * FROM gallery2 WHERE topic_id="897596" UNION SELECT * FROM gallery2 WHERE topic_id="1308161" UNION SELECT * FROM gallery2 WHERE topic_id="1453484" UNION SELECT * FROM gallery2 WHERE topic_id="1553134" UNION SELECT * FROM gallery2 WHERE topic_id="192878"