You have to choose

SELECT * FROM gallery2 WHERE topic_id="1412743" UNION SELECT * FROM gallery2 WHERE topic_id="1624287" UNION SELECT * FROM gallery2 WHERE topic_id="424752" UNION SELECT * FROM gallery2 WHERE topic_id="712641" UNION SELECT * FROM gallery2 WHERE topic_id="629009" UNION SELECT * FROM gallery2 WHERE topic_id="1729261" UNION SELECT * FROM gallery2 WHERE topic_id="1326980" UNION SELECT * FROM gallery2 WHERE topic_id="106251" UNION SELECT * FROM gallery2 WHERE topic_id="369574" UNION SELECT * FROM gallery2 WHERE topic_id="203125" UNION SELECT * FROM gallery2 WHERE topic_id="965495" UNION SELECT * FROM gallery2 WHERE topic_id="36358" UNION SELECT * FROM gallery2 WHERE topic_id="448135" UNION SELECT * FROM gallery2 WHERE topic_id="1351865" UNION SELECT * FROM gallery2 WHERE topic_id="1155785" UNION SELECT * FROM gallery2 WHERE topic_id="1090618"