You clearly have done something wrong

SELECT * FROM gallery2 WHERE topic_id="262578" UNION SELECT * FROM gallery2 WHERE topic_id="1797727" UNION SELECT * FROM gallery2 WHERE topic_id="1623366" UNION SELECT * FROM gallery2 WHERE topic_id="75016" UNION SELECT * FROM gallery2 WHERE topic_id="1618499" UNION SELECT * FROM gallery2 WHERE topic_id="1027944" UNION SELECT * FROM gallery2 WHERE topic_id="1230971" UNION SELECT * FROM gallery2 WHERE topic_id="101957" UNION SELECT * FROM gallery2 WHERE topic_id="1477274" UNION SELECT * FROM gallery2 WHERE topic_id="1716279" UNION SELECT * FROM gallery2 WHERE topic_id="1536677" UNION SELECT * FROM gallery2 WHERE topic_id="561965" UNION SELECT * FROM gallery2 WHERE topic_id="100538" UNION SELECT * FROM gallery2 WHERE topic_id="385195" UNION SELECT * FROM gallery2 WHERE topic_id="684253" UNION SELECT * FROM gallery2 WHERE topic_id="326033"