Question

我有一张像这样的表：

+----+---------+----------+
| id | group   | value    |
+----+---------+----------+
|  1 | GROUP A | 0.641028 | 
|  2 | GROUP B | 0.946927 | 
|  3 | GROUP A | 0.811552 | 
|  4 | GROUP C | 0.216978 | 
|  5 | GROUP A | 0.650232 | 
+----+---------+----------+

如果我执行以下查询：

SELECT `id`, SUM(`value`) AS `sum` FROM `test` GROUP BY `group`;

我，显然，得到：

+----+-------------------+
| id | sum               |
+----+-------------------+
|  1 |  2.10281205177307 | 
|  2 | 0.946927309036255 | 
|  4 | 0.216977506875992 | 
+----+-------------------+

但我需要一张像这样的表：

+----+-------------------+
| id | sum               |
+----+-------------------+
|  1 |  2.10281205177307 | 
|  2 | 0.946927309036255 | 
|  3 |  2.10281205177307 | 
|  4 | 0.216977506875992 | 
|  5 |  2.10281205177307 | 
+----+-------------------+

明确重复求和的行。

有没有办法在不使用多个（嵌套）查询的情况下获得此结果？

Answer 1

IT将依赖于您的SQL服务器，在Postgres / Oracle中我会使用Window Functions。在MySQL中......不可能是afaik。

也许你可以这样假装：

SELECT a.id, SUM(b.value) AS `sum`
FROM test AS a
JOIN test AS b ON a.`group` = b.`group`
GROUP BY a.id, b.`group`;

Answer 2

没有AFAIK。你必须使用像

这样的连接

SELECT t.`id`, tsum.sum AS `sum`
FROM `test` as t GROUP BY `group`
JOIN (SELECT `id`, SUM(`value`) AS `sum` FROM `test` GROUP BY `group`) AS tsum
     ON tsum.id = t.id

如何在不将结果分组到SQL的情况下应用SUM操作？

2 个答案: