在PostgreSQL中选择数组列的总和

Question

如果我有下表:

Table "users"
Column          |       Type       | Modifiers 
---------------+------------------+-----------
  id            | integer          | not null default nextval('users_id_seq'::regclass)
  monthly_usage | real[]           | 

monthly_usage12个数字的数组在哪里,即{1.2, 1.3, 6.2, 0.9,...}

如何选择该列的总和？

有点像:

SELECT id, sum(monthly_usage) as total_usage from users;

这显然不起作用.

Answer 1

SELECT id, (SELECT SUM(s) FROM UNNEST(monthly_usage) s) as total_usage from users;

Answer 2

这种概括和重新格式化Dmitry的答案有助于我理解它的工作原理：

SELECT
  sum(a) AS total
FROM
  (
    SELECT
      unnest(array [1,2,3]) AS a
  ) AS b

结果：

total
 6