MySQL 有限结果后的一行求和

Question

我有这个User表:

+----------+-------+
| Username | Value |
+----------+-------+
| User4    |     2 |
| User1    |     3 |
| User3    |     1 |
| User2    |     6 |
| User4    |     2 |
+----------+-------+

我执行此查询来获取前 2 个的总和:

SELECT Username, SUM(Value) AS Sum
FROM User
GROUP BY Username
ORDER BY Sum DESC
LIMIT 0, 2

这给了我结果:

+----------+-----+
| Username | Sum |
+----------+-----+
| User2    |   6 |
| User4    |   4 |
+----------+-----+

我正在寻找的是再一行给出所有值的总和，例如:

+----------+-----+
| Username | Sum |
+----------+-----+
| User2    |   6 |
| User4    |   4 |
| All      |  14 |
+----------+-----+

有什么办法可以实现这一点吗？最好没有任何程序。

Answer 1

您可以使用WITH ROLLUP修饰符:

SELECT COALESCE(Username, 'All'), SUM(Value) AS Sum
FROM User
GROUP BY Username WITH ROLLUP
ORDER BY Sum DESC 

或者，如果您只想要前 2 个以及所有的总和:

 SELECT Username, s
 FROM (
    SELECT Username, s
    FROM (
      SELECT COALESCE(Username, 'All') AS Username, SUM(Value) AS s
      FROM User
      GROUP BY Username WITH ROLLUP  ) AS t
    ORDER BY s DESC      
    LIMIT 0, 3) AS s
 ORDER BY IF(Username = 'All', 0, s) DESC