mysql 去重累加

mysql去重累加可以使用以下SQL语句：

SELECT SUM(c) 
FROM (
    SELECT COUNT(DISTINCT column_name) c 
    FROM table_name 
    WHERE conditions
    UNION ALL 
    SELECT COUNT(DISTINCT column_name) c 
    FROM table_name 
    WHERE conditions
) AS temp;

其中，`column_name`是需要去重累加的列名，`table_name`是需要查询的表名，`conditions`是查询条件。