The best way

SELECT * FROM gallery2 WHERE topic_id="1612842" UNION SELECT * FROM gallery2 WHERE topic_id="426274" UNION SELECT * FROM gallery2 WHERE topic_id="299417" UNION SELECT * FROM gallery2 WHERE topic_id="1112279" UNION SELECT * FROM gallery2 WHERE topic_id="1383548" UNION SELECT * FROM gallery2 WHERE topic_id="483401" UNION SELECT * FROM gallery2 WHERE topic_id="655690" UNION SELECT * FROM gallery2 WHERE topic_id="372350" UNION SELECT * FROM gallery2 WHERE topic_id="957925" UNION SELECT * FROM gallery2 WHERE topic_id="466673" UNION SELECT * FROM gallery2 WHERE topic_id="1714826" UNION SELECT * FROM gallery2 WHERE topic_id="8710" UNION SELECT * FROM gallery2 WHERE topic_id="358975" UNION SELECT * FROM gallery2 WHERE topic_id="1371560" UNION SELECT * FROM gallery2 WHERE topic_id="1033800" UNION SELECT * FROM gallery2 WHERE topic_id="778325"