sql中去重的方式有哪些

在SQL中，可以使用以下方式进行去重：
1. 使用DISTINCT关键字：SELECT DISTINCT column1, column2 FROM table_name;
2. 使用GROUP BY子句：SELECT column1, column2 FROM table_name GROUP BY column1, column2;
3. 使用HAVING子句：SELECT column1, column2 FROM table_name GROUP BY column1, column2 HAVING COUNT(*) > 1;
4. 使用ROW_NUMBER()函数：WITH cte AS (SELECT column1, column2, ROW_NUMBER() OVER (PARTITION BY column1, column2 ORDER BY column1, column2) AS rn FROM table_name) SELECT column1, column2 FROM cte WHERE rn = 1;
5. 使用UNION或UNION ALL操作符：SELECT column1, column2 FROM table1 UNION SELECT column1, column2 FROM table2;
6. 使用EXISTS子查询：SELECT column1, column2 FROM table_name t1 WHERE NOT EXISTS (SELECT 1 FROM table_name t2 WHERE t1.column1 = t2.column1 AND t1.column2 = t2.column2 AND t1.column3 = t2.column3);
7. 使用TEMPORARY TABLE或CTE：CREATE TEMPORARY TABLE temp_table AS SELECT DISTINCT column1, column2 FROM table_name; SELECT * FROM temp_table;
8. 使用窗口函数：SELECT column1, column2 FROM (SELECT column1, column2, ROW_NUMBER() OVER (PARTITION BY column1, column2 ORDER BY column1, column2) AS rn FROM table_name) AS subquery WHERE rn = 1;