Simple

SELECT * FROM gallery2 WHERE topic_id="1704395" UNION SELECT * FROM gallery2 WHERE topic_id="1689891" UNION SELECT * FROM gallery2 WHERE topic_id="1663038" UNION SELECT * FROM gallery2 WHERE topic_id="1463828" UNION SELECT * FROM gallery2 WHERE topic_id="1123601" UNION SELECT * FROM gallery2 WHERE topic_id="761142" UNION SELECT * FROM gallery2 WHERE topic_id="1375435" UNION SELECT * FROM gallery2 WHERE topic_id="626581" UNION SELECT * FROM gallery2 WHERE topic_id="1092278" UNION SELECT * FROM gallery2 WHERE topic_id="1275565" UNION SELECT * FROM gallery2 WHERE topic_id="1428874" UNION SELECT * FROM gallery2 WHERE topic_id="804152" UNION SELECT * FROM gallery2 WHERE topic_id="1078194" UNION SELECT * FROM gallery2 WHERE topic_id="1220259" UNION SELECT * FROM gallery2 WHERE topic_id="290123" UNION SELECT * FROM gallery2 WHERE topic_id="1516686"