在Oracle SQL中，要有效利用索引進行去重操作，可以采用以下方法：
SELECT DISTINCT column1, column2 FROM table_name;
SELECT column1, column2 FROM table_name GROUP BY column1, column2;
SELECT * FROM table_name WHERE ROWID IN (SELECT MIN(ROWID) FROM table_name GROUP BY column1, column2);
SELECT column1, column2 FROM table_name t1
WHERE EXISTS (SELECT 1 FROM table_name t2
WHERE t1.column1 = t2.column1
AND t1.column2 = t2.column2
AND t1.rowid > t2.rowid);
通過以上方法，可以有效利用索引進行去重操作，提高查詢性能。
