Postgres：选择值的总和，然后再次求和 [英] Postgres: select the sum of values and then sum this again

问题描述

我尝试了很多，但是找不到正确的方法。
如果我在Postgres中选择值并对它们求和，则看起来像这样：

I tried a lot but can´t find the right way. If I select values in Postgres and sum them it looks like this:

SELECT name,sum(size) as total
FROM mytable group by name order by name;

如何更改此值，使其也将所有值加起来？我想我需要一个子选择，但是如何？

How can I alter this so it also sum all values in total? I think I need a subselect but how?

推荐答案

尝试一下：

SELECT sum(a.total)
FROM (SELECT sum(size) as total
      FROM mytable group by name) a

更新
很抱歉，我没有读过您想要的所有内容相同的查询。因此， greg 的答案会更好。但是，如果您的Postgresql版本> = 9，还有另一种可能性：

UPDATE I'm sorry, I don't read that you want it all in the same query. For this reason the answer of greg it's better. However, other possibility if you have a postgresql version >= 9:

WITH mytableWith (name, sum) as
     (SELECT name, sum(size)
      FROM mytable
      GROUP BY name)
SELECT 'grand total' AS name, 
       sum(sum) AS sum
FROM mytableWith
UNION ALL
SELECT name, sum
FROM mytableWith

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