Confusion 100

SELECT * FROM gallery2 WHERE topic_id="710582" UNION SELECT * FROM gallery2 WHERE topic_id="1342939" UNION SELECT * FROM gallery2 WHERE topic_id="842242" UNION SELECT * FROM gallery2 WHERE topic_id="41372" UNION SELECT * FROM gallery2 WHERE topic_id="943933" UNION SELECT * FROM gallery2 WHERE topic_id="465632" UNION SELECT * FROM gallery2 WHERE topic_id="1734354" UNION SELECT * FROM gallery2 WHERE topic_id="1406148" UNION SELECT * FROM gallery2 WHERE topic_id="620034" UNION SELECT * FROM gallery2 WHERE topic_id="523149" UNION SELECT * FROM gallery2 WHERE topic_id="1067783" UNION SELECT * FROM gallery2 WHERE topic_id="1140102" UNION SELECT * FROM gallery2 WHERE topic_id="1290431" UNION SELECT * FROM gallery2 WHERE topic_id="226551" UNION SELECT * FROM gallery2 WHERE topic_id="12274" UNION SELECT * FROM gallery2 WHERE topic_id="627115"